perl58delta.1 manual page -- Interix / SUA

Interix / SUA

perl58delta.1

Interix / SUA

PERL58DELTA(1) Perl Programmers Reference Guide PERL58DELTA(1)

NAME
perl58delta - what is new for perl v5.8.0

DESCRIPTION
This document describes differences between the 5.6.0
release and the 5.8.0 release.

Many of the bug fixes in 5.8.0 were already seen in the
5.6.1 maintenance release since the two releases were kept
closely coordinated (while 5.8.0 was still called
5.7.something).

Changes that were integrated into the 5.6.1 release are
marked "[561]". Many of these changes have been further
developed since 5.6.1 was released, those are marked
"[561+]".

You can see the list of changes in the 5.6.1 release (both
from the 5.005_03 release and the 5.6.0 release) by read-
ing perl561delta.

Highlights In 5.8.0
o Better Unicode support

o New IO Implementation

o New Thread Implementation

o Better Numeric Accuracy

o Safe Signals

o Many New Modules

o More Extensive Regression Testing

Incompatible Changes
Binary Incompatibility

Perl 5.8 is not binary compatible with earlier releases of
Perl.

You have to recompile your XS modules.

(Pure Perl modules should continue to work.)

The major reason for the discontinuity is the new IO
architecture called PerlIO. PerlIO is the default config-
uration because without it many new features of Perl 5.8
cannot be used. In other words: you just have to recom-
pile your modules containing XS code, sorry about that.

In future releases of Perl, non-PerlIO aware XS modules
may become completely unsupported. This shouldn't be too
difficult for module authors, however: PerlIO has been
designed as a drop-in replacement (at the source code
level) for the stdio interface.

Depending on your platform, there are also other reasons
why we decided to break binary compatibility, please read
on.

64-bit platforms and malloc

If your pointers are 64 bits wide, the Perl malloc is no
longer being used because it does not work well with
8-byte pointers. Also, usually the system mallocs on such
platforms are much better optimized for such large memory
models than the Perl malloc. Some memory-hungry Perl
applications like the PDL don't work well with Perl's mal-
loc. Finally, other applications than Perl (such as
mod_perl) tend to prefer the system malloc. Such plat-
forms include Alpha and 64-bit HPPA, MIPS, PPC, and Sparc.

AIX Dynaloading

The AIX dynaloading now uses in AIX releases 4.3 and newer
the native dlopen interface of AIX instead of the old emu-
lated interface. This change will probably break backward
compatibility with compiled modules. The change was made
to make Perl more compliant with other applications like
mod_perl which are using the AIX native interface.

Attributes for "my" variables now handled at run-time

The "my EXPR : ATTRS" syntax now applies variable
attributes at run-time. (Subroutine and "our" variables
still get attributes applied at compile-time.) See
attributes for additional details. In particular, how-
ever, this allows variable attributes to be useful for
"tie" interfaces, which was a deficiency of earlier
releases. Note that the new semantics doesn't work with
the Attribute::Handlers module (as of version 0.76).

Socket Extension Dynamic in VMS

The Socket extension is now dynamically loaded instead of
being statically built in. This may or may not be a prob-
lem with ancient TCP/IP stacks of VMS: we do not know
since we weren't able to test Perl in such configurations.

IEEE-format Floating Point Default on OpenVMS Alpha

Perl now uses IEEE format (T_FLOAT) as the default inter-
nal floating point format on OpenVMS Alpha, potentially
breaking binary compatibility with external libraries or
existing data. G_FLOAT is still available as a configura-
tion option. The default on VAX (D_FLOAT) has not
changed.

New Unicode Semantics (no more "use utf8", almost)

Previously in Perl 5.6 to use Unicode one would say "use
utf8" and then the operations (like string concatenation)
were Unicode-aware in that lexical scope.

This was found to be an inconvenient interface, and in
Perl 5.8 the Unicode model has completely changed: now the
"Unicodeness" is bound to the data itself, and for most of
the time "use utf8" is not needed at all. The only
remaining use of "use utf8" is when the Perl script itself
has been written in the UTF-8 encoding of Unicode. (UTF-8
has not been made the default since there are many Perl
scripts out there that are using various national eight-
bit character sets, which would be illegal in UTF-8.)

See perluniintro for the explanation of the current model,
and utf8 for the current use of the utf8 pragma.

New Unicode Properties

Unicode scripts are now supported. Scripts are similar to
(and superior to) Unicode blocks. The difference between
scripts and blocks is that scripts are the glyphs used by
a language or a group of languages, while the blocks are
more artificial groupings of (mostly) 256 characters based
on the Unicode numbering.

In general, scripts are more inclusive, but not univer-
sally so. For example, while the script "Latin" includes
all the Latin characters and their various diacritic-
adorned versions, it does not include the various punctua-
tion or digits (since they are not solely "Latin").

A number of other properties are now supported, including
"\p{L&}", "\p{Any}" "\p{Assigned}", "\p{Unassigned}",
"\p{Blank}" [561] and "\p{SpacePerl}" [561] (along with
their "\P{...}" versions, of course). See perlunicode for
details, and more additions.

The "In" or "Is" prefix to names used with the "\p{...}"
and "\P{...}" are now almost always optional. The only
exception is that a "In" prefix is required to signify a
Unicode block when a block name conflicts with a script
name. For example, "\p{Tibetan}" refers to the script,
while "\p{InTibetan}" refers to the block. When there is
no name conflict, you can omit the "In" from the block
name (e.g. "\p{BraillePatterns}"), but to be safe, it's
probably best to always use the "In").

REF(...) Instead Of SCALAR(...)

A reference to a reference now stringifies as
"REF(0x81485ec)" instead of "SCALAR(0x81485ec)" in order
to be more consistent with the return value of ref().

pack/unpack D/F recycled

The undocumented pack/unpack template letters D/F have
been recycled for better use: now they stand for long dou-
ble (if supported by the platform) and NV (Perl internal
floating point type). (They used to be aliases for d/f,
but you never knew that.)

glob() now returns filenames in alphabetical order

The list of filenames from glob() (or <...>) is now by
default sorted alphabetically to be csh-compliant (which
is what happened before in most UNIX platforms).
(bsd_glob() does still sort platform natively, ASCII or
EBCDIC, unless GLOB_ALPHASORT is specified.) [561]

Deprecations

o The semantics of bless(REF, REF) were unclear and
until someone proves it to make some sense, it is for-
bidden.

o The obsolete chat2 library that should never have been
allowed to escape the laboratory has been decommis-
sioned.

o Using chdir("") or chdir(undef) instead of explicit
chdir() is doubtful. A failure (think
chdir(some_function()) can lead into unintended
chdir() to the home directory, therefore this
behaviour is deprecated.

o The builtin dump() function has probably outlived most
of its usefulness. The core-dumping functionality
will remain in future available as an explicit call to
"CORE::dump()", but in future releases the behaviour
of an unqualified "dump()" call may change.

o The very dusty examples in the eg/ directory have been
removed. Suggestions for new shiny examples welcome
but the main issue is that the examples need to be
documented, tested and (most importantly) maintained.

o The (bogus) escape sequences \8 and \9 now give an
optional warning ("Unrecognized escape passed
through"). There is no need to \-escape any "\w"
character.

o The *glob{FILEHANDLE} is deprecated, use *glob{IO}
instead.

o The "package;" syntax ("package" without an argument)
has been deprecated. Its semantics were never that
clear and its implementation even less so. If you
have used that feature to disallow all but fully qual-
ified variables, "use strict;" instead.

o The unimplemented POSIX regex features [[.cc.]] and
[[=c=]] are still recognised but now cause fatal
errors. The previous behaviour of ignoring them by
default and warning if requested was unacceptable
since it, in a way, falsely promised that the features
could be used.

o In future releases, non-PerlIO aware XS modules may
become completely unsupported. Since PerlIO is a
drop-in replacement for stdio at the source code
level, this shouldn't be that drastic a change.

o Previous versions of perl and some readings of some
sections of Camel III implied that the ":raw" "disci-
pline" was the inverse of ":crlf". Turning off "clrf-
ness" is no longer enough to make a stream truly
binary. So the PerlIO ":raw" layer (or "discipline",
to use the Camel book's older terminology) is now for-
mally defined as being equivalent to binmode(FH) -
which is in turn defined as doing whatever is neces-
sary to pass each byte as-is without any translation.
In particular binmode(FH) - and hence ":raw" - will
now turn off both CRLF and UTF-8 translation and
remove other layers (e.g. :encoding()) which would
modify byte stream.

o The current user-visible implementation of pseudo-
hashes (the weird use of the first array element) is
deprecated starting from Perl 5.8.0 and will be
removed in Perl 5.10.0, and the feature will be imple-
mented differently. Not only is the current interface
rather ugly, but the current implementation slows down
normal array and hash use quite noticeably. The
"fields" pragma interface will remain available. The
restricted hashes interface is expected to be the
replacement interface (see Hash::Util). If your
existing programs depends on the underlying implemen-
tation, consider using Class::PseudoHash from CPAN.

o The syntaxes "@a->[...]" and "%h->{...}" have now
been deprecated.

o After years of trying, suidperl is considered to be
too complex to ever be considered truly secure. The
suidperl functionality is likely to be removed in a
future release.

o The 5.005 threads model (module "Thread") is depre-
cated and expected to be removed in Perl 5.10. Multi-
threaded code should be migrated to the new ithreads
model (see threads, threads::shared and perlthrtut).

o The long deprecated uppercase aliases for the string
comparison operators (EQ, NE, LT, LE, GE, GT) have now
been removed.

o The tr///C and tr///U features have been removed and
will not return; the interface was a mistake. Sorry
about that. For similar functionality, see pack('U0',
...) and pack('C0', ...). [561]

o Earlier Perls treated "sub foo (@bar)" as equivalent
to "sub foo (@)". The prototypes are now checked bet-
ter at compile-time for invalid syntax. An optional
warning is generated ("Illegal character in proto-
type...") but this may be upgraded to a fatal error
in a future release.

o The "exec LIST" and "system LIST" operations now pro-
duce warnings on tainted data and in some future
release they will produce fatal errors.

o The existing behaviour when localising tied arrays and
hashes is wrong, and will be changed in a future
release, so do not rely on the existing behaviour. See
"Localising Tied Arrays and Hashes Is Broken".

Core Enhancements
Unicode Overhaul

Unicode in general should be now much more usable than in
Perl 5.6.0 (or even in 5.6.1). Unicode can be used in
hash keys, Unicode in regular expressions should work now,
Unicode in tr/// should work now, Unicode in I/O should
work now. See perluniintro for introduction and perluni-
code for details.

o The Unicode Character Database coming with Perl has
been upgraded to Unicode 3.2.0. For more information,
see http://www.unicode.org/ . [561+] (5.6.1 has UCD
3.0.1.)

o For developers interested in enhancing Perl's Unicode
capabilities: almost all the UCD files are included
with the Perl distribution in the lib/unicore subdi-
rectory. The most notable omission, for space consid-
erations, is the Unihan database.

o The properties \p{Blank} and \p{SpacePerl} have been
added. "Blank" is like C isblank(), that is, it con-
tains only "horizontal whitespace" (the space
character is, the newline isn't), and the "SpacePerl"
is the Unicode equivalent of "\s" (\p{Space} isn't,
since that includes the vertical tabulator character,
whereas "\s" doesn't.)

See "New Unicode Properties" earlier in this document
for additional information on changes with Unicode
properties.

PerlIO is Now The Default

o IO is now by default done via PerlIO rather than sys-
tem's "stdio". PerlIO allows "layers" to be "pushed"
onto a file handle to alter the handle's behaviour.
Layers can be specified at open time via 3-arg form of
open:

open($fh,'>:crlf :utf8', $path) || ...

or on already opened handles via extended "binmode":

binmode($fh,':encoding(iso-8859-7)');

The built-in layers are: unix (low level read/write),
stdio (as in previous Perls), perlio (re-implementa-
tion of stdio buffering in a portable manner), crlf
(does CRLF <=> "\n" translation as on Win32, but
available on any platform). A mmap layer may be
available if platform supports it (mostly UNIXes).

Layers to be applied by default may be specified via
the 'open' pragma.

See "Installation and Configuration Improvements" for
the effects of PerlIO on your architecture name.

o If your platform supports fork(), you can use the list
form of "open" for pipes. For example:

open KID_PS, "-|", "ps", "aux" or die $!;

forks the ps(1) command (without spawning a shell, as
there are more than three arguments to open()), and
reads its standard output via the "KID_PS" filehandle.
See perlipc.

o File handles can be marked as accepting Perl's inter-
nal encoding of Unicode (UTF-8 or UTF-EBCDIC depending
on platform) by a pseudo layer ":utf8" :

open($fh,">:utf8","Uni.txt");

Note for EBCDIC users: the pseudo layer ":utf8" is
erroneously named for you since it's not UTF-8 what
you will be getting but instead UTF-EBCDIC. See per-
lunicode, utf8, and http://www.unicode.org/uni-
code/reports/tr16/ for more information. In future
releases this naming may change. See perluniintro for
more information about UTF-8.

o If your environment variables (LC_ALL, LC_CTYPE, LANG)
look like you want to use UTF-8 (any of the variables
match "/utf-?8/i"), your STDIN, STDOUT, STDERR handles
and the default open layer (see open) are marked as
UTF-8. (This feature, like other new features that
combine Unicode and I/O, work only if you are using
PerlIO, but that's the default.)

Note that after this Perl really does assume that
everything is UTF-8: for example if some input handle
is not, Perl will probably very soon complain about
the input data like this "Malformed UTF-8 ..." since
any old eight-bit data is not legal UTF-8.

Note for code authors: if you want to enable your
users to use UTF-8 as their default encoding but in
your code still have eight-bit I/O streams (such as
images or zip files), you need to explicitly open() or
binmode() with ":bytes" (see "open" in perlfunc and
"binmode" in perlfunc), or you can just use "bin-
mode(FH)" (nice for pre-5.8.0 backward compatibility).

o File handles can translate character encodings from/to
Perl's internal Unicode form on read/write via the
":encoding()" layer.

o File handles can be opened to "in memory" files held
in Perl scalars via:

open($fh,'>', \$variable) || ...

o Anonymous temporary files are available without need
to 'use FileHandle' or other module via

open($fh,"+>", undef) || ...

That is a literal undef, not an undefined value.

ithreads

The new interpreter threads ("ithreads" for short) imple-
mentation of multithreading, by Arthur Bergman, replaces
the old "5.005 threads" implementation. In the ithreads
model any data sharing between threads must be explicit,
as opposed to the model where data sharing was implicit.
See threads and threads::shared, and perlthrtut.

As a part of the ithreads implementation Perl will also
use any necessary and detectable reentrant libc inter-
faces.

Restricted Hashes

A restricted hash is restricted to a certain set of keys,
no keys outside the set can be added. Also individual
keys can be restricted so that the key cannot be deleted
and the value cannot be changed. No new syntax is
involved: the Hash::Util module is the interface.

Safe Signals

Perl used to be fragile in that signals arriving at inop-
portune moments could corrupt Perl's internal state. Now
Perl postpones handling of signals until it's safe
(between opcodes).

This change may have surprising side effects because sig-
nals no longer interrupt Perl instantly. Perl will now
first finish whatever it was doing, like finishing an
internal operation (like sort()) or an external operation
(like an I/O operation), and only then look at any arrived
signals (and before starting the next operation). No more
corrupt internal state since the current operation is
always finished first, but the signal may take more time
to get heard. Note that breaking out from potentially
blocking operations should still work, though.

Understanding of Numbers

In general a lot of fixing has happened in the area of
Perl's understanding of numbers, both integer and floating
point. Since in many systems the standard number parsing
functions like "strtoul()" and "atof()" seem to have bugs,
Perl tries to work around their deficiencies. This
results hopefully in more accurate numbers.

Perl now tries internally to use integer values in numeric
conversions and basic arithmetics (+ - * /) if the argu-
ments are integers, and tries also to keep the results
stored internally as integers. This change leads to often
slightly faster and always less lossy arithmetics. (Previ-
ously Perl always preferred floating point numbers in its
math.)

Arrays now always interpolate into double-quoted strings
[561]

In double-quoted strings, arrays now interpolate, no mat-
ter what. The behavior in earlier versions of perl 5 was
that arrays would interpolate into strings if the array
had been mentioned before the string was compiled, and
otherwise Perl would raise a fatal compile-time error. In
versions 5.000 through 5.003, the error was

Literal @example now requires backslash

In versions 5.004_01 through 5.6.0, the error was

In string, @example now must be written as \@example

The idea here was to get people into the habit of writing
"fred\@example.com" when they wanted a literal "@" sign,
just as they have always written "Give me back my \$5"
when they wanted a literal "$" sign.

Starting with 5.6.1, when Perl now sees an "@" sign in a
double-quoted string, it always attempts to interpolate an
array, regardless of whether or not the array has been
used or declared already. The fatal error has been down-
graded to an optional warning:

Possible unintended interpolation of @example in string

This warns you that "fred@example.com" is going to turn
into "fred.com" if you don't backslash the "@". See
http://www.plover.com/~mjd/perl/at-error.html for more
details about the history here.

Miscellaneous Changes

o AUTOLOAD is now lvaluable, meaning that you can add
the :lvalue attribute to AUTOLOAD subroutines and you
can assign to the AUTOLOAD return value.

o The $Config{byteorder} (and corresponding BYTEORDER in
config.h) was previously wrong in platforms if
sizeof(long) was 4, but sizeof(IV) was 8. The byte-
order was only sizeof(long) bytes long (1234 or 4321),
but now it is correctly sizeof(IV) bytes long,
(12345678 or 87654321). (This problem didn't affect
Windows platforms.)

Also, $Config{byteorder} is now computed dynami-
cally--this is more robust with "fat binaries" where
an executable image contains binaries for more than
one binary platform, and when cross-compiling.

o "perl -d:Module=arg,arg,arg" now works (previously one
couldn't pass in multiple arguments.)

o "do" followed by a bareword now ensures that this
bareword isn't a keyword (to avoid a bug where "do
q(foo.pl)" tried to call a subroutine called "q").
This means that for example instead of "do format()"
you must write "do &format()".

o The builtin dump() now gives an optional warning
"dump() better written as CORE::dump()", meaning that
by default "dump(...)" is resolved as the builtin
dump() which dumps core and aborts, not as (possibly)
user-defined "sub dump". To call the latter, qualify
the call as "&dump(...)". (The whole dump() feature
is to considered deprecated, and possibly
removed/changed in future releases.)

o chomp() and chop() are now overridable. Note, how-
ever, that their prototype (as given by "proto-
type("CORE::chomp")" is undefined, because it cannot
be expressed and therefore one cannot really write
replacements to override these builtins.

o END blocks are now run even if you exit/die in a BEGIN
block. Internally, the execution of END blocks is now
controlled by PL_exit_flags & PERL_EXIT_DESTRUCT_END.
This enables the new behaviour for Perl embedders.
This will default in 5.10. See perlembed.

o Formats now support zero-padded decimal fields.

o Although "you shouldn't do that", it was possible to
write code that depends on Perl's hashed key order
(Data::Dumper does this). The new algorithm
"One-at-a-Time" produces a different hashed key order.
More details are in "Performance Enhancements".

o lstat(FILEHANDLE) now gives a warning because the
operation makes no sense. In future releases this may
become a fatal error.

o Spurious syntax errors generated in certain situa-
tions, when glob() caused File::Glob to be loaded for
the first time, have been fixed. [561]

o Lvalue subroutines can now return "undef" in list con-
text. However, the lvalue subroutine feature still
remains experimental. [561+]

o A lost warning "Can't declare ... dereference in my"
has been restored (Perl had it earlier but it became
lost in later releases.)

o A new special regular expression variable has been
introduced: $^N, which contains the most-recently
closed group (submatch).

o "no Module;" does not produce an error even if Module
does not have an unimport() method. This parallels
the behavior of "use" vis-a-vis "import". [561]

o The numerical comparison operators return "undef" if
either operand is a NaN. Previously the behaviour was
unspecified.

o "our" can now have an experimental optional attribute
"unique" that affects how global variables are shared
among multiple interpreters, see "our" in perlfunc.

o The following builtin functions are now overridable:
each(), keys(), pop(), push(), shift(), splice(),
unshift(). [561]

o "pack() / unpack()" can now group template letters
with "()" and then apply repetition/count modifiers on
the groups.

o "pack() / unpack()" can now process the Perl internal
numeric types: IVs, UVs, NVs-- and also long doubles,
if supported by the platform. The template letters
are "j", "J", "F", and "D".

o "pack('U0a*', ...)" can now be used to force a string
to UTF-8.

o my __PACKAGE__ $obj now works. [561]

o POSIX::sleep() now returns the number of unslept sec-
onds (as the POSIX standard says), as opposed to
CORE::sleep() which returns the number of slept sec-
onds.

o printf() and sprintf() now support parameter reorder-
ing using the "%\d+\$" and "*\d+\$" syntaxes. For
example

printf "%2\$s %1\$s\n", "foo", "bar";

will print "bar foo\n". This feature helps in writing
internationalised software, and in general when the
order of the parameters can vary.

o The (\&) prototype now works properly. [561]

o prototype(\[$@%&]) is now available to implicitly cre-
ate references (useful for example if you want to emu-
late the tie() interface).

o A new command-line option, "-t" is available. It is
the little brother of "-T": instead of dying on taint
violations, lexical warnings are given. This is only
meant as a temporary debugging aid while securing the
code of old legacy applications. This is not a sub-
stitute for -T.

o In other taint news, the "exec LIST" and "system LIST"
have now been considered too risky (think "exec
@ARGV": it can start any program with any arguments),
and now the said forms cause a warning under lexical
warnings. You should carefully launder the arguments
to guarantee their validity. In future releases of
Perl the forms will become fatal errors so consider
starting laundering now.

o Tied hash interfaces are now required to have the
EXISTS and DELETE methods (either own or inherited).

o If tr/// is just counting characters, it doesn't
attempt to modify its target.

o untie() will now call an UNTIE() hook if it exists.
See perltie for details. [561]

o utime now supports "utime undef, undef, @files" to
change the file timestamps to the current time.

o The rules for allowing underscores (underbars) in
numeric constants have been relaxed and simplified:
now you can have an underscore simply between digits.

o Rather than relying on C's argv[0] (which may not con-
tain a full pathname) where possible $^X is now set by
asking the operating system. (eg by reading
/proc/self/exe on Linux, /proc/curproc/file on
FreeBSD)

o A new variable, "${^TAINT}", indicates whether taint
mode is enabled.

o You can now override the readline() builtin, and this
overrides also the angle bracket opera-
tor.

o The command-line options -s and -F are now recognized
on the shebang (#!) line.

o Use of the "/c" match modifier without an accompanying
"/g" modifier elicits a new warning: "Use of /c modi-
fier is meaningless without /g".

Use of "/c" in substitutions, even with "/g", elicits
"Use of /c modifier is meaningless in s///".

Use of "/g" with "split" elicits "Use of /g modifier
is meaningless in split".

o Support for the "CLONE" special subroutine had been
added. With ithreads, when a new thread is created,
all Perl data is cloned, however non-Perl data cannot
be cloned automatically. In "CLONE" you can do what-
ever you need to do, like for example handle the
cloning of non-Perl data, if necessary. "CLONE" will
be executed once for every package that has it defined
or inherited. It will be called in the context of the
new thread, so all modifications are made in the new
area.

See perlmod

Modules and Pragmata
New Modules and Pragmata

o "Attribute::Handlers", originally by Damian Conway and
now maintained by Arthur Bergman, allows a class to
define attribute handlers.

package MyPack;
use Attribute::Handlers;
sub Wolf :ATTR(SCALAR) { print "howl!\n" }

# later, in some package using or inheriting from MyPack...

my MyPack $Fluffy : Wolf; # the attribute handler Wolf will be called

Both variables and routines can have attribute han-
dlers. Handlers can be specific to type (SCALAR,
ARRAY, HASH, or CODE), or specific to the exact compi-
lation phase (BEGIN, CHECK, INIT, or END). See
Attribute::Handlers.

o "B::Concise", by Stephen McCamant, is a new compiler
backend for walking the Perl syntax tree, printing
concise info about ops. The output is highly cus-
tomisable. See B::Concise. [561+]

o The new bignum, bigint, and bigrat pragmas, by Tels,
implement transparent bignum support (using the
Math::BigInt, Math::BigFloat, and Math::BigRat back-
ends).

o "Class::ISA", by Sean Burke, is a module for reporting
the search path for a class's ISA tree. See
Class::ISA.

o "Cwd" now has a split personality: if possible, an XS
extension is used, (this will hopefully be faster,
more secure, and more robust) but if not possible, the
familiar Perl implementation is used.

o "Devel::PPPort", originally by Kenneth Albanowski and
now maintained by Paul Marquess, has been added. It
is primarily used by "h2xs" to enhance portability of
XS modules between different versions of Perl. See
Devel::PPPort.

o "Digest", frontend module for calculating digests
(checksums), from Gisle Aas, has been added. See
Digest.

o "Digest::MD5" for calculating MD5 digests (checksums)
as defined in RFC 1321, from Gisle Aas, has been
added. See Digest::MD5.

use Digest::MD5 'md5_hex';

$digest = md5_hex("Thirsty Camel");

print $digest, "\n"; # 01d19d9d2045e005c3f1b80e8b164de1

NOTE: the "MD5" backward compatibility module is
deliberately not included since its further use is
discouraged.

See also PerlIO::via::QuotedPrint.

o "NEXT", by Damian Conway, is a pseudo-class for method
redispatch. See NEXT.

o "open" is a new pragma for setting the default I/O
layers for open().

o "PerlIO::scalar", by Nick Ing-Simmons, provides the
implementation of IO to "in memory" Perl scalars as
discussed above. It also serves as an example of a
loadable PerlIO layer. Other future possibilities
include PerlIO::Array and PerlIO::Code. See Per-
lIO::scalar.

o "PerlIO::via", by Nick Ing-Simmons, acts as a PerlIO
layer and wraps PerlIO layer functionality provided by
a class (typically implemented in Perl code).

o "PerlIO::via::QuotedPrint", by Elizabeth Mattijsen, is
an example of a "PerlIO::via" class:

use PerlIO::via::QuotedPrint;
open($fh,">:via(QuotedPrint)",$path);

This will automatically convert everything output to
$fh to Quoted-Printable. See PerlIO::via and Per-
lIO::via::QuotedPrint.

o "Pod::ParseLink", by Russ Allbery, has been added, to
parse L<> links in pods as described in the new
perlpodspec.

o "Pod::Text::Overstrike", by Joe Smith, has been added.
It converts POD data to formatted overstrike text.
See Pod::Text::Overstrike. [561+]

o "Scalar::Util" is a selection of general-utility
scalar subroutines, such as blessed(), reftype(), and
tainted(). See Scalar::Util.

o "sort" is a new pragma for controlling the behaviour
of sort().

o "Storable" gives persistence to Perl data structures
by allowing the storage and retrieval of Perl data to
and from files in a fast and compact binary format.
Because in effect Storable does serialisation of Perl
data structures, with it you can also clone deep,
hierarchical datastructures. Storable was originally
created by Raphael Manfredi, but it is now maintained
by Abhijit Menon-Sen. Storable has been enhanced to
understand the two new hash features, Unicode keys and
restricted hashes. See Storable.

o "Switch", by Damian Conway, has been added. Just by
saying

use Switch;

you have "switch" and "case" available in Perl.

use Switch;

switch ($val) {

case 1 { print "number 1" }
case "a" { print "string a" }
case [1..10,42] { print "number in list" }
case (@array) { print "number in list" }
case /\w+/ { print "pattern" }
case qr/\w+/ { print "pattern" }
case (%hash) { print "entry in hash" }
case (\%hash) { print "entry in hash" }
case (\&sub) { print "arg to subroutine" }
else { print "previous case not true" }
}

See Switch.

o "Test::More", by Michael Schwern, is yet another
framework for writing test scripts, more extensive
than Test::Simple. See Test::More.

o "Test::Simple", by Michael Schwern, has basic utili-
ties for writing tests. See Test::Simple.

o "Text::Balanced", by Damian Conway, has been added,
for extracting delimited text sequences from strings.

use Text::Balanced 'extract_delimited';

($a, $b) = extract_delimited("'never say never', he never said", "'", '');

$a will be "'never say never'", $b will be ', he never
said'.

In addition to extract_delimited(), there are also
extract_bracketed(), extract_quotelike(),
extract_codeblock(), extract_variable(),
extract_tagged(), extract_multiple(), gen_delim-
ited_pat(), and gen_extract_tagged(). With these, you
can implement rather advanced parsing algorithms. See
Text::Balanced.

o "threads", by Arthur Bergman, is an interface to
interpreter threads. Interpreter threads (ithreads)
is the new thread model introduced in Perl 5.6 but
only available as an internal interface for extension
writers (and for Win32 Perl for "fork()" emulation).
See threads, threads::shared, and perlthrtut.

o "threads::shared", by Arthur Bergman, allows data
sharing for interpreter threads. See threads::shared.

o "Tie::File", by Mark-Jason Dominus, associates a Perl
array with the lines of a file. See Tie::File.

o "Tie::Memoize", by Ilya Zakharevich, provides on-
demand loaded hashes. See Tie::Memoize.

o "Tie::RefHash::Nestable", by Edward Avis, allows stor-
ing hash references (unlike the standard Tie::RefHash)
The module is contained within Tie::RefHash. See
Tie::RefHash.

o "Time::HiRes", by Douglas E. Wegscheid, provides high
resolution timing (ualarm, usleep, and gettimeofday).
See Time::HiRes.

o "Unicode::UCD" offers a querying interface to the Uni-
code Character Database. See Unicode::UCD.

o "Unicode::Collate", by SADAHIRO Tomoyuki, implements
the UCA (Unicode Collation Algorithm) for sorting Uni-
code strings. See Unicode::Collate.

o "Unicode::Normalize", by SADAHIRO Tomoyuki, implements
the various Unicode normalization forms. See Uni-
code::Normalize.

o "XS::APItest", by Tim Jenness, is a test extension
that exercises XS APIs. Currently only "printf()" is
tested: how to output various basic data types from
XS.

o "XS::Typemap", by Tim Jenness, is a test extension
that exercises XS typemaps. Nothing gets installed,
but the code is worth studying for extension writers.

Updated And Improved Modules and Pragmata

o The following independently supported modules have
been updated to the newest versions from CPAN: CGI,
CPAN, DB_File, File::Spec, File::Temp, Getopt::Long,
Math::BigFloat, Math::BigInt, the podlators bundle
(Pod::Man, Pod::Text), Pod::LaTeX [561+], Pod::Parser,
Storable, Term::ANSIColor, Test, Text-Tabs+Wrap.

o attributes::reftype() now works on tied arguments.

o AutoLoader can now be disabled with "no AutoLoader;".

o B::Deparse has been significantly enhanced by Robin
Houston. It can now deparse almost all of the stan-
dard test suite (so that the tests still succeed).
There is a make target "test.deparse" for trying this
out.

o Carp now has better interface documentation, and the
@CARP_NOT interface has been added to get optional
control over where errors are reported independently
of @ISA, by Ben Tilly.

o Class::Struct can now define the classes in compile
time.

o Class::Struct now assigns the array/hash element if
the accessor is called with an array/hash element as
the sole argument.

o The return value of Cwd::fastcwd() is now tainted.

o Data::Dumper now has an option to sort hashes.

o Data::Dumper now has an option to dump code references
using B::Deparse.

o DB_File now supports newer Berkeley DB versions, among
other improvements.

o Devel::Peek now has an interface for the Perl memory
statistics (this works only if you are using perl's
malloc, and if you have compiled with debugging).

o The English module can now be used without the infa-
mous performance hit by saying

use English '-no_match_vars';

(Assuming, of course, that you don't need the trouble-
some variables $`, $&, or $'.) Also, introduced
@LAST_MATCH_START and @LAST_MATCH_END English aliases
for "@-" and "@+".

o ExtUtils::MakeMaker has been significantly cleaned up
and fixed. The enhanced version has also been back-
ported to earlier releases of Perl and submitted to
CPAN so that the earlier releases can enjoy the fixes.

o The arguments of WriteMakefile() in Makefile.PL are
now checked for sanity much more carefully than
before. This may cause new warnings when modules are
being installed. See ExtUtils::MakeMaker for more
details.

o ExtUtils::MakeMaker now uses File::Spec internally,
which hopefully leads to better portability.

o Fcntl, Socket, and Sys::Syslog have been rewritten by
Nicholas Clark to use the new-style constant dispatch
section (see ExtUtils::Constant). This means that
they will be more robust and hopefully faster.

o File::Find now chdir()s correctly when chasing sym-
bolic links. [561]

o File::Find now has pre- and post-processing callbacks.
It also correctly changes directories when chasing
symbolic links. Callbacks (naughtily) exiting with
"next;" instead of "return;" now work.

o File::Find is now (again) reentrant. It also has been
made more portable.

o The warnings issued by File::Find now belong to their
own category. You can enable/disable them with
"use/no warnings 'File::Find';".

o File::Glob::glob() has been renamed to
File::Glob::bsd_glob() because the name clashes with
the builtin glob(). The older name is still available
for compatibility, but is deprecated. [561]

o File::Glob now supports "GLOB_LIMIT" constant to limit
the size of the returned list of filenames.

o IPC::Open3 now allows the use of numeric file descrip-
tors.

o IO::Socket now has an atmark() method, which returns
true if the socket is positioned at the out-of-band
mark. The method is also exportable as a sockatmark()
function.

o IO::Socket::INET failed to open the specified port if
the service name was not known. It now correctly uses
the supplied port number as is. [561]

o IO::Socket::INET has support for the ReusePort option
(if your platform supports it). The Reuse option now
has an alias, ReuseAddr. For clarity, you may want to
prefer ReuseAddr.

o IO::Socket::INET now supports a value of zero for
"LocalPort" (usually meaning that the operating system
will make one up.)

o 'use lib' now works identically to @INC. Removing
directories with 'no lib' now works.

o Math::BigFloat and Math::BigInt have undergone a full
rewrite by Tels. They are now magnitudes faster, and
they support various bignum libraries such as GMP and
PARI as their backends.

o Math::Complex handles inf, NaN etc., better.

o Net::Ping has been considerably enhanced by Rob Brown:
multihoming is now supported, Win32 functionality is
better, there is now time measuring functionality
(optionally high-resolution using Time::HiRes), and
there is now "external" protocol which uses
Net::Ping::External module which runs your external
ping utility and parses the output. A version of
Net::Ping::External is available in CPAN.

Note that some of the Net::Ping tests are disabled
when running under the Perl distribution since one
cannot assume one or more of the following: enabled
echo port at localhost, full Internet connectivity, or
sympathetic firewalls. You can set the environment
variable PERL_TEST_Net_Ping to "1" (one) before run-
ning the Perl test suite to enable all the Net::Ping
tests.

o POSIX::sigaction() is now much more flexible and
robust. You can now install coderef handlers,
'DEFAULT', and 'IGNORE' handlers, installing new han-
dlers was not atomic.

o In Safe, %INC is now localised in a Safe compartment
so that use/require work.

o In SDBM_File on dosish platforms, some keys went miss-
ing because of lack of support for files with "holes".
A workaround for the problem has been added.

o In Search::Dict one can now have a pre-processing hook
for the lines being searched.

o The Shell module now has an OO interface.

o In Sys::Syslog there is now a failover mechanism that
will go through alternative connection mechanisms
until the message is successfully logged.

o The Test module has been significantly enhanced.

o Time::Local::timelocal() does not handle fractional
seconds anymore. The rationale is that neither does
localtime(), and timelocal() and localtime() are sup-
posed to be inverses of each other.

o The vars pragma now supports declaring fully qualified
variables. (Something that "our()" does not and will
not support.)

o The "utf8::" name space (as in the pragma) provides
various Perl-callable functions to provide low level
access to Perl's internal Unicode representation. At
the moment only length() has been implemented.

Utility Changes
o Emacs perl mode (emacs/cperl-mode.el) has been updated
to version 4.31.

o emacs/e2ctags.pl is now much faster.

o "enc2xs" is a tool for people adding their own encod-
ings to the Encode module.

o "h2ph" now supports C trigraphs.

o "h2xs" now produces a template README.

o "h2xs" now uses "Devel::PPPort" for better portability
between different versions of Perl.

o "h2xs" uses the new ExtUtils::Constant module which
will affect newly created extensions that define con-
stants. Since the new code is more correct (if you
have two constants where the first one is a prefix of
the second one, the first constant never got defined),
less lossy (it uses integers for integer constant, as
opposed to the old code that used floating point num-
bers even for integer constants), and slightly faster,
you might want to consider regenerating your extension
code (the new scheme makes regenerating easy). h2xs
now also supports C trigraphs.

o "libnetcfg" has been added to configure libnet.

o "perlbug" is now much more robust. It also sends the
bug report to perl.org, not perl.com.

o "perlcc" has been rewritten and its user interface
(that is, command line) is much more like that of the
UNIX C compiler, cc. (The perlbc tools has been
removed. Use "perlcc -B" instead.) Note that perlcc
is still considered very experimental and unsupported.
[561]

o "perlivp" is a new Installation Verification Procedure
utility for running any time after installing Perl.

o "piconv" is an implementation of the character conver-
sion utility "iconv", demonstrating the new Encode
module.

o "pod2html" now allows specifying a cache directory.

o "pod2html" now produces XHTML 1.0.

o "pod2html" now understands POD written using different
line endings (PC-like CRLF versus UNIX-like LF versus
MacClassic-like CR).

o "s2p" has been completely rewritten in Perl. (It is
in fact a full implementation of sed in Perl: you can
use the sed functionality by using the "psed" util-
ity.)

o "xsubpp" now understands POD documentation embedded in
the *.xs files. [561]

o "xsubpp" now supports the OUT keyword.

New Documentation
o perl56delta details the changes between the 5.005
release and the 5.6.0 release.

o perlclib documents the internal replacements for stan-
dard C library functions. (Interesting only for
extension writers and Perl core hackers.) [561+]

o perldebtut is a Perl debugging tutorial. [561+]

o perlebcdic contains considerations for running Perl on
EBCDIC platforms. [561+]

o perlintro is a gentle introduction to Perl.

o perliol documents the internals of PerlIO with layers.

o perlmodstyle is a style guide for writing modules.

o perlnewmod tells about writing and submitting a new
module. [561+]

o perlpacktut is a pack() tutorial.

o perlpod has been rewritten to be clearer and to record
the best practices gathered over the years.

o perlpodspec is a more formal specification of the pod
format, mainly of interest for writers of pod applica-
tions, not to people writing in pod.

o perlretut is a regular expression tutorial. [561+]

o perlrequick is a regular expressions quick-start
guide. Yes, much quicker than perlretut. [561]

o perltodo has been updated.

o perltootc has been renamed as perltooc (to not to con-
flict with perltoot in filesystems restricted to "8.3"
names).

o perluniintro is an introduction to using Unicode in
Perl. (perlunicode is more of a detailed reference
and background information)

o perlutil explains the command line utilities packaged
with the Perl distribution. [561+]

The following platform-specific documents are available
before the installation as README.platform, and after the
installation as perlplatform:

perlaix perlamiga perlapollo perlbeos perlbs2000
perlce perlcygwin perldgux perldos perlepoc perlfreebsd perlhpux
perlhurd perlirix perlmachten perlmacos perlmint perlmpeix
perlnetware perlos2 perlos390 perlplan9 perlqnx perlsolaris
perltru64 perluts perlvmesa perlvms perlvos perlwin32

These documents usually detail one or more of the follow-
ing subjects: configuring, building, testing, installing,
and sometimes also using Perl on the said platform.

Eastern Asian Perl users are now welcomed in their own
languages: README.jp (Japanese), README.ko (Korean),
README.cn (simplified Chinese) and README.tw (traditional
Chinese), which are written in normal pod but encoded in
EUC-JP, EUC-KR, EUC-CN and Big5. These will get installed
as

perljp perlko perlcn perltw

o The documentation for the POSIX-BC platform is called
"BS2000", to avoid confusion with the Perl POSIX mod-
ule.

o The documentation for the WinCE platform is called
perlce (README.ce in the source code kit), to avoid
confusion with the perlwin32 documentation on
8.3-restricted filesystems.

Performance Enhancements
o map() could get pathologically slow when the result
list it generates is larger than the source list. The
performance has been improved for common scenarios.
[561]

o sort() is also fully reentrant, in the sense that the
sort function can itself call sort(). This did not
work reliably in previous releases. [561]

o sort() has been changed to use primarily mergesort
internally as opposed to the earlier quicksort. For
very small lists this may result in slightly slower
sorting times, but in general the speedup should be at
least 20%. Additional bonuses are that the worst case
behaviour of sort() is now better (in computer science
terms it now runs in time O(N log N), as opposed to
quicksort's Theta(N**2) worst-case run time
behaviour), and that sort() is now stable (meaning
that elements with identical keys will stay ordered as
they were before the sort). See the "sort" pragma for
information.

The story in more detail: suppose you want to serve
yourself a little slice of Pi.

@digits = ( 3,1,4,1,5,9 );

A numerical sort of the digits will yield
(1,1,3,4,5,9), as expected. Which 1 comes first is
hard to know, since one 1 looks pretty much like any
other. You can regard this as totally trivial, or
somewhat profound. However, if you just want to sort
the even digits ahead of the odd ones, then what will

sort { ($a % 2) <=> ($b % 2) } @digits;

yield? The only even digit, 4, will come first. But
how about the odd numbers, which all compare equal?
With the quicksort algorithm used to implement Perl
5.6 and earlier, the order of ties is left up to the
sort. So, as you add more and more digits of Pi, the
order in which the sorted even and odd digits appear
will change. and, for sufficiently large slices of
Pi, the quicksort algorithm in Perl 5.8 won't return
the same results even if reinvoked with the same
input. The justification for this rests with quick-
sort's worst case behavior. If you run

sort { $a <=> $b } ( 1 .. $N , 1 .. $N );

(something you might approximate if you wanted to
merge two sorted arrays using sort), doubling $N
doesn't just double the quicksort time, it quadruples
it. Quicksort has a worst case run time that can grow
like N**2, so-called quadratic behaviour, and it can
happen on patterns that may well arise in normal use.
You won't notice this for small arrays, but you will
notice it with larger arrays, and you may not live
long enough for the sort to complete on arrays of a
million elements. So the 5.8 quicksort scrambles
large arrays before sorting them, as a statistical
defence against quadratic behaviour. But that means
if you sort the same large array twice, ties may be
broken in different ways.

Because of the unpredictability of tie-breaking order,
and the quadratic worst-case behaviour, quicksort was
almost replaced completely with a stable mergesort.
Stable means that ties are broken to preserve the
original order of appearance in the input array. So

sort { ($a % 2) <=> ($b % 2) } (3,1,4,1,5,9);

will yield (4,3,1,1,5,9), guaranteed. The even and
odd numbers appear in the output in the same order
they appeared in the input. Mergesort has worst case
O(N log N) behaviour, the best value attainable. And,
ironically, this mergesort does particularly well
where quicksort goes quadratic: mergesort sorts
(1..$N, 1..$N) in O(N) time. But quicksort was res-
cued at the last moment because it is faster than
mergesort on certain inputs and platforms. For exam-
ple, if you really don't care about the order of even
and odd digits, quicksort will run in O(N) time; it's
very good at sorting many repetitions of a small num-
ber of distinct elements. The quicksort divide and
conquer strategy works well on platforms with rela-
tively small, very fast, caches. Eventually, the
problem gets whittled down to one that fits in the
cache, from which point it benefits from the increased
memory speed.

Quicksort was rescued by implementing a sort pragma to
control aspects of the sort. The stable subpragma
forces stable behaviour, regardless of algorithm. The
_quicksort and _mergesort subpragmas are heavy-handed
ways to select the underlying implementation. The
leading "_" is a reminder that these subpragmas may
not survive beyond 5.8. More appropriate mechanisms
for selecting the implementation exist, but they
wouldn't have arrived in time to save quicksort.

o Hashes now use Bob Jenkins "One-at-a-Time" hashing key
algorithm ( http://burtlebur-
tle.net/bob/hash/doobs.html ). This algorithm is rea-
sonably fast while producing a much better spread of
values than the old hashing algorithm (originally by
Chris Torek, later tweaked by Ilya Zakharevich). Hash
values output from the algorithm on a hash of all
3-char printable ASCII keys comes much closer to pass-
ing the DIEHARD random number generation tests.
According to perlbench, this change has not affected
the overall speed of Perl.

o unshift() should now be noticeably faster.

Installation and Configuration Improvements
Generic Improvements

o INSTALL now explains how you can configure Perl to use
64-bit integers even on non-64-bit platforms.

o Policy.sh policy change: if you are reusing a Pol-
icy.sh file (see INSTALL) and you use Configure -Dpre-
fix=/foo/bar and in the old Policy $prefix eq
$siteprefix and $prefix eq $vendorprefix, all of them
will now be changed to the new prefix, /foo/bar.
(Previously only $prefix changed.) If you do not like
this new behaviour, specify prefix, siteprefix, and
vendorprefix explicitly.

o A new optional location for Perl libraries, otherlib-
dirs, is available. It can be used for example for
vendor add-ons without disturbing Perl's own library
directories.

o In many platforms, the vendor-supplied 'cc' is too
stripped-down to build Perl (basically, 'cc' doesn't
do ANSI C). If this seems to be the case and 'cc'
does not seem to be the GNU C compiler 'gcc', an auto-
matic attempt is made to find and use 'gcc' instead.

o gcc needs to closely track the operating system
release to avoid build problems. If Configure finds
that gcc was built for a different operating system
release than is running, it now gives a clearly visi-
ble warning that there may be trouble ahead.

o Since Perl 5.8 is not binary-compatible with previous
releases of Perl, Configure no longer suggests includ-
ing the 5.005 modules in @INC.

o Configure "-S" can now run non-interactively. [561]

o Configure support for pdp11-style memory models has
been removed due to obsolescence. [561]

o configure.gnu now works with options with whitespace
in them.

o installperl now outputs everything to STDERR.

o Because PerlIO is now the default on most platforms,
"-perlio" doesn't get appended to the $Config{arch-
name} (also known as $^O) anymore. Instead, if you
explicitly choose not to use perlio (Configure command
line option -Uuseperlio), you will get "-stdio"
appended.

o Another change related to the architecture name is
that "-64all" (-Duse64bitall, or "maximally 64-bit")
is appended only if your pointers are 64 bits wide.
(To be exact, the use64bitall is ignored.)

o In AFS installations, one can configure the root of
the AFS to be somewhere else than the default /afs by
using the Configure parameter "-Dafs-
root=/some/where/else".

o APPLLIB_EXP, a lesser-known configuration-time defini-
tion, has been documented. It can be used to prepend
site-specific directories to Perl's default search
path (@INC); see INSTALL for information.

o The version of Berkeley DB used when the Perl (and,
presumably, the DB_File extension) was built is now
available as @Config{qw(db_version_major db_ver-
sion_minor db_version_patch)} from Perl and as
"DB_VERSION_MAJOR_CFG DB_VERSION_MINOR_CFG DB_VER-
SION_PATCH_CFG" from C.

o Building Berkeley DB3 for compatibility modes for DB,
NDBM, and ODBM has been documented in INSTALL.

o If you have CPAN access (either network or a local
copy such as a CD-ROM) you can during specify extra
modules to Configure to build and install with Perl
using the -Dextras=... option. See INSTALL for more
details.

o In addition to config.over, a new override file, con-
fig.arch, is available. This file is supposed to be
used by hints file writers for architecture-wide
changes (as opposed to config.over which is for site-
wide changes).

o If your file system supports symbolic links, you can
build Perl outside of the source directory by

mkdir perl/build/directory
cd perl/build/directory
sh /path/to/perl/source/Configure -Dmksymlinks ...

This will create in perl/build/directory a tree of
symbolic links pointing to files in
/path/to/perl/source. The original files are left
unaffected. After Configure has finished, you can
just say

make all test

and Perl will be built and tested, all in
perl/build/directory. [561]

o For Perl developers, several new make targets for pro-
filing and debugging have been added; see perlhack.

o Use of the gprof tool to profile Perl has been
documented in perlhack. There is a make tar-
get called "perl.gprof" for generating a gpro-
filed Perl executable.

o If you have GCC 3, there is a make target
called "perl.gcov" for creating a gcoved Perl
executable for coverage analysis. See perl-
hack.

o If you are on IRIX or Tru64 platforms, new
profiling/debugging options have been added;
see perlhack for more information about pixie
and Third Degree.

o Guidelines of how to construct minimal Perl installa-
tions have been added to INSTALL.

o The Thread extension is now not built at all under
ithreads ("Configure -Duseithreads") because it
wouldn't work anyway (the Thread extension requires
being Configured with "-Duse5005threads").

Note that the 5.005 threads are unsupported and depre-
cated: if you have code written for the old threads
you should migrate it to the new ithreads model.

o The Gconvert macro ($Config{d_Gconvert}) used by perl
for stringifying floating-point numbers is now more
picky about using sprintf %.*g rules for the conver-
sion. Some platforms that used to use gcvt may now
resort to the slower sprintf.

o The obsolete method of making a special (e.g., debug-
ging) flavor of perl by saying

make LIBPERL=libperld.a

has been removed. Use -DDEBUGGING instead.

New Or Improved Platforms

For the list of platforms known to support Perl, see "Sup-
ported Platforms" in perlport.

o AIX dynamic loading should be now better supported.

o AIX should now work better with gcc, threads, and
64-bitness. Also the long doubles support in AIX
should be better now. See perlaix.

o AtheOS ( http://www.atheos.cx/ ) is a new platform.

o BeOS has been reclaimed.

o The DG/UX platform now supports 5.005-style threads.
See perldgux.

o The DYNIX/ptx platform (also known as dynixptx) is
supported at or near osvers 4.5.2.

o EBCDIC platforms (z/OS (also known as OS/390),
POSIX-BC, and VM/ESA) have been regained. Many test
suite tests still fail and the co-existence of Unicode
and EBCDIC isn't quite settled, but the situation is
much better than with Perl 5.6. See perlos390,
perlbs2000 (for POSIX-BC), and perlvmesa for more
information.

o Building perl with -Duseithreads or -Duse5005threads
now works under HP-UX 10.20 (previously it only worked
under 10.30 or later). You will need a thread library
package installed. See README.hpux. [561]

o Mac OS Classic is now supported in the mainstream
source package (MacPerl has of course been available
since perl 5.004 but now the source code bases of
standard Perl and MacPerl have been synchronised)
[561]

o Mac OS X (or Darwin) should now be able to build Perl
even on HFS+ filesystems. (The case-insensitivity
used to confuse the Perl build process.)

o NCR MP-RAS is now supported. [561]

o All the NetBSD specific patches (except for the
installation specific ones) have been merged back to
the main distribution.

o NetWare from Novell is now supported. See perlnet-
ware.

o NonStop-UX is now supported. [561]

o NEC SUPER-UX is now supported.

o All the OpenBSD specific patches (except for the
installation specific ones) have been merged back to
the main distribution.

o Perl has been tested with the GNU pth userlevel thread
package ( http://www.gnu.org/software/pth/pth.html ).
All thread tests of Perl now work, but not without
adding some yield()s to the tests, so while pth (and
other userlevel thread implementations) can be consid-
ered to be "working" with Perl ithreads, keep in mind
the possible non-preemptability of the underlying
thread implementation.

o Stratus VOS is now supported using Perl's native build
method (Configure). This is the recommended method to
build Perl on VOS. The older methods, which build
miniperl, are still available. See perlvos. [561+]

o The Amdahl UTS UNIX mainframe platform is now sup-
ported. [561]

o WinCE is now supported. See perlce.

o z/OS (formerly known as OS/390, formerly known as MVS
OE) now has support for dynamic loading. This is not
selected by default, however, you must specify -Dusedl
in the arguments of Configure. [561]

Selected Bug Fixes
Numerous memory leaks and uninitialized memory accesses
have been hunted down. Most importantly, anonymous subs
used to leak quite a bit. [561]

o The autouse pragma didn't work for Multi::Part::Func-
tion::Names.

o caller() could cause core dumps in certain situations.
Carp was sometimes affected by this problem. In par-
ticular, caller() now returns a subroutine name of
"(unknown)" for subroutines that have been removed
from the symbol table.

o chop(@list) in list context returned the characters
chopped in reverse order. This has been reversed to
be in the right order. [561]

o Configure no longer includes the DBM libraries (dbm,
gdbm, db, ndbm) when building the Perl binary. The
only exception to this is SunOS 4.x, which needs them.
[561]

o The behaviour of non-decimal but numeric string
constants such as "0x23" was platform-dependent: in
some platforms that was seen as 35, in some as 0, in
some as a floating point number (don't ask). This was
caused by Perl's using the operating system libraries
in a situation where the result of the string to num-
ber conversion is undefined: now Perl consistently
handles such strings as zero in numeric contexts.

o Several debugger fixes: exit code now reflects the
script exit code, condition "0" now treated correctly,
the "d" command now checks line number, $. no longer
gets corrupted, and all debugger output now goes cor-
rectly to the socket if RemotePort is set. [561]

o The debugger (perl5db.pl) has been modified to present
a more consistent commands interface, via (Command-
Set=580). perl5db.t was also added to test the
changes, and as a placeholder for further tests.

See perldebug.

o The debugger has a new "dumpDepth" option to control
the maximum depth to which nested structures are
dumped. The "x" command has been extended so that "x
N EXPR" dumps out the value of EXPR to a depth of at
most N levels.

o The debugger can now show lexical variables if you
have the CPAN module PadWalker installed.

o The order of DESTROYs has been made more predictable.

o Perl 5.6.0 could emit spurious warnings about redefi-
nition of dl_error() when statically building exten-
sions into perl. This has been corrected. [561]

o dprofpp -R didn't work.

o *foo{FORMAT} now works.

o Infinity is now recognized as a number.

o UNIVERSAL::isa no longer caches methods incorrectly.
(This broke the Tk extension with 5.6.0.) [561]

o Lexicals I: lexicals outside an eval "" weren't
resolved correctly inside a subroutine definition
inside the eval "" if they were not already referenced
in the top level of the eval""ed code.

o Lexicals II: lexicals leaked at file scope into sub-
routines that were declared before the lexicals.

o Lexical warnings now propagating correctly between
scopes and into "eval "..."".

o "use warnings qw(FATAL all)" did not work as intended.
This has been corrected. [561]

o warnings::enabled() now reports the state of $^W cor-
rectly if the caller isn't using lexical warnings.
[561]

o Line renumbering with eval and "#line" now works.
[561]

o Fixed numerous memory leaks, especially in eval "".

o Localised tied variables no longer leak memory

use Tie::Hash;
tie my %tied_hash => 'Tie::StdHash';

...

# Used to leak memory every time local() was called;
# in a loop, this added up.
local($tied_hash{Foo}) = 1;

o Localised hash elements (and %ENV) are correctly unlo-
calised to not exist, if they didn't before they were
localised.

use Tie::Hash;
tie my %tied_hash => 'Tie::StdHash';

...

# Nothing has set the FOO element so far

{ local $tied_hash{FOO} = 'Bar' }

# This used to print, but not now.
print "exists!\n" if exists $tied_hash{FOO};

As a side effect of this fix, tied hash interfaces
must define the EXISTS and DELETE methods.

o mkdir() now ignores trailing slashes in the directory
name, as mandated by POSIX.

o Some versions of glibc have a broken modfl(). This
affects builds with "-Duselongdouble". This version
of Perl detects this brokenness and has a workaround
for it. The glibc release 2.2.2 is known to have
fixed the modfl() bug.

o Modulus of unsigned numbers now works (4063328477 %
65535 used to return 27406, instead of 27047). [561]

o Some "not a number" warnings introduced in 5.6.0 elim-
inated to be more compatible with 5.005. Infinity is
now recognised as a number. [561]

o Numeric conversions did not recognize changes in the
string value properly in certain circumstances. [561]

o Attributes (such as :shared) didn't work with our().

o our() variables will not cause bogus "Variable will
not stay shared" warnings. [561]

o "our" variables of the same name declared in two sib-
ling blocks resulted in bogus warnings about "redecla-
ration" of the variables. The problem has been cor-
rected. [561]

o pack "Z" now correctly terminates the string with
"\0".

o Fix password routines which in some shadow password
platforms (e.g. HP-UX) caused getpwent() to return
every other entry.

o The PERL5OPT environment variable (for passing command
line arguments to Perl) didn't work for more than a
single group of options. [561]

o PERL5OPT with embedded spaces didn't work.

o printf() no longer resets the numeric locale to "C".

o "qw(a\\b)" now parses correctly as 'a\\b': that is, as
three characters, not four. [561]

o pos() did not return the correct value within s///ge
in earlier versions. This is now handled correctly.
[561]

o Printing quads (64-bit integers) with printf/sprintf
now works without the q L ll prefixes (assuming you
are on a quad-capable platform).

o Regular expressions on references and overloaded
scalars now work. [561+]

o Right-hand side magic (GMAGIC) could in many cases
such as string concatenation be invoked too many
times.

o scalar() now forces scalar context even when used in
void context.

o SOCKS support is now much more robust.

o sort() arguments are now compiled in the right wantar-
ray context (they were accidentally using the context
of the sort() itself). The comparison block is now
run in scalar context, and the arguments to be sorted
are always provided list context. [561]

o Changed the POSIX character class "[[:space:]]" to
include the (very rarely used) vertical tab character.
Added a new POSIX-ish character class "[[:blank:]]"
which stands for horizontal whitespace (currently, the
space and the tab).

o The tainting behaviour of sprintf() has been rational-
ized. It does not taint the result of floating point
formats anymore, making the behaviour consistent with
that of string interpolation. [561]

o Some cases of inconsistent taint propagation (such as
within hash values) have been fixed.

o The RE engine found in Perl 5.6.0 accidentally pes-
simised certain kinds of simple pattern matches.
These are now handled better. [561]

o Regular expression debug output (whether through "use
re 'debug'" or via "-Dr") now looks better. [561]

o Multi-line matches like ""a\nxb\n" =~ /(?!\A)x/m" were
flawed. The bug has been fixed. [561]

o Use of $& could trigger a core dump under some situa-
tions. This is now avoided. [561]

o The regular expression captured submatches ($1, $2,
...) are now more consistently unset if the match
fails, instead of leaving false data lying around in
them. [561]

o readline() on files opened in "slurp" mode could
return an extra "" (blank line) at the end in certain
situations. This has been corrected. [561]

o Autovivification of symbolic references of special
variables described in perlvar (as in "${$num}") was
accidentally disabled. This works again now. [561]

o Sys::Syslog ignored the "LOG_AUTH" constant.

o $AUTOLOAD, sort(), lock(), and spawning subprocesses
in multiple threads simultaneously are now
thread-safe.

o Tie::Array's SPLICE method was broken.

o Allow a read-only string on the left-hand side of a
non-modifying tr///.

o If "STDERR" is tied, warnings caused by "warn" and
"die" now correctly pass to it.

o Several Unicode fixes.

o BOMs (byte order marks) at the beginning of
Perl files (scripts, modules) should now be
transparently skipped. UTF-16 and UCS-2
encoded Perl files should now be read cor-
rectly.

o The character tables have been updated to Uni-
code 3.2.0.

o Comparing with utf8 data does not magically
upgrade non-utf8 data into utf8. (This was a
problem for example if you were mixing data
from I/O and Unicode data: your output might
have got magically encoded as UTF-8.)

o Generating illegal Unicode code points such as
U+FFFE, or the UTF-16 surrogates, now also
generates an optional warning.

o "IsAlnum", "IsAlpha", and "IsWord" now match
titlecase.

o Concatenation with the "." operator or via
variable interpolation, "eq", "substr",
"reverse", "quotemeta", the "x" operator, sub-
stitution with "s///", single-quoted UTF-8,
should now work.

o The "tr///" operator now works. Note that the
"tr///CU" functionality has been removed (but
see pack('U0', ...)).

o "eval "v200"" now works.

o Perl 5.6.0 parsed m/\x{ab}/ incorrectly, lead-
ing to spurious warnings. This has been cor-
rected. [561]

o Zero entries were missing from the Unicode
classes such as "IsDigit".

o Large unsigned numbers (those above 2**31) could some-
times lose their unsignedness, causing bogus results
in arithmetic operations. [561]

o The Perl parser has been stress tested using both ran-
dom input and Markov chain input and the few found
crashes and lockups have been fixed.

Platform Specific Changes and Fixes

o BSDI 4.*

Perl now works on post-4.0 BSD/OSes.

o All BSDs

Setting $0 now works (as much as possible; see perlvar
for details).

o Cygwin

Numerous updates; currently synchronised with Cygwin
1.3.10.

o Previously DYNIX/ptx had problems in its Configure
probe for non-blocking I/O.

o EPOC

EPOC now better supported. See README.epoc. [561]

o FreeBSD 3.*

Perl now works on post-3.0 FreeBSDs.

o HP-UX

README.hpux updated; "Configure -Duse64bitall" now
works; now uses HP-UX malloc instead of Perl malloc.

o IRIX

Numerous compilation flag and hint enhancements; acci-
dental mixing of 32-bit and 64-bit libraries (a doomed
attempt) made much harder.

o Linux

o Long doubles should now work (see INSTALL).
[561]

o Linux previously had problems related to sock-
addrlen when using accept(), recvfrom() (in
Perl: recv()), getpeername(), and getsock-
name().

o Mac OS Classic

Compilation of the standard Perl distribution in Mac
OS Classic should now work if you have the Metrowerks
development environment and the missing Mac-specific
toolkit bits. Contact the macperl mailing list for
details.

o MPE/iX

MPE/iX update after Perl 5.6.0. See README.mpeix.
[561]

o NetBSD/threads: try installing the GNU pth (should be
in the packages collection, or
http://www.gnu.org/software/pth/), and Configure with
-Duseithreads.

o NetBSD/sparc

Perl now works on NetBSD/sparc.

o OS/2

Now works with usethreads (see INSTALL). [561]

o Solaris

64-bitness using the Sun Workshop compiler now works.

o Stratus VOS

The native build method requires at least VOS Release
14.5.0 and GNU C++/GNU Tools 2.0.1 or later. The Perl
pack function now maps overflowed values to +infinity
and underflowed values to -infinity.

o Tru64 (aka Digital UNIX, aka DEC OSF/1)

The operating system version letter now recorded in
$Config{osvers}. Allow compiling with gcc (previously
explicitly forbidden). Compiling with gcc still not
recommended because buggy code results, even with gcc
2.95.2.

o Unicos

Fixed various alignment problems that lead into core
dumps either during build or later; no longer dies on
math errors at runtime; now using full quad integers
(64 bits), previously was using only 46 bit integers
for speed.

o VMS

See "Socket Extension Dynamic in VMS" and "IEEE-format
Floating Point Default on OpenVMS Alpha" for important
changes not otherwise listed here.

chdir() now works better despite a CRT bug; now works
with MULTIPLICITY (see INSTALL); now works with Perl's
malloc.

The tainting of %ENV elements via "keys" or "values"
was previously unimplemented. It now works as docu-
mented.

The "waitpid" emulation has been improved. The worst
bug (now fixed) was that a pid of -1 would cause a
wildcard search of all processes on the system.

POSIX-style signals are now emulated much better on
VMS versions prior to 7.0.

The "system" function and backticks operator have
improved functionality and better error handling.
[561]

File access tests now use current process privileges
rather than the user's default privileges, which could
sometimes result in a mismatch between reported access
and actual access. This improvement is only available
on VMS v6.0 and later.

There is a new "kill" implementation based on
"sys$sigprc" that allows older VMS systems (pre-7.0)
to use "kill" to send signals rather than simply force
exit. This implementation also allows later systems
to call "kill" from within a signal handler.

Iterative logical name translations are now limited to
10 iterations in imitation of SHOW LOGICAL and other
OpenVMS facilities.

o Windows

o Signal handling now works better than it used
to. It is now implemented using a Windows
message loop, and is therefore less prone to
random crashes.

o fork() emulation is now more robust, but still
continues to have a few esoteric bugs and
caveats. See perlfork for details. [561+]

o A failed (pseudo)fork now returns undef and
sets errno to EAGAIN. [561]

o The following modules now work on Windows:

ExtUtils::Embed [561]
IO::Pipe
IO::Poll
Net::Ping

o IO::File::new_tmpfile() is no longer limited
to 32767 invocations per-process.

o Better chdir() return value for a non-existent
directory.

o Compiling perl using the 64-bit Platform SDK
tools is now supported.

o The Win32::SetChildShowWindow() builtin can be
used to control the visibility of windows cre-
ated by child processes. See Win32 for
details.

o Non-blocking waits for child processes (or
pseudo-processes) are supported via "wait-
pid($pid, &POSIX::WNOHANG)".

o The behavior of system() with multiple argu-
ments has been rationalized. Each unquoted
argument will be automatically quoted to pro-
tect whitespace, and any existing whitespace
in the arguments will be preserved. This
improves the portability of system(@args) by
avoiding the need for Windows "cmd" shell spe-
cific quoting in perl programs.

Note that this means that some scripts that
may have relied on earlier buggy behavior may
no longer work correctly. For example, "sys-
tem("nmake /nologo", @args)" will now attempt
to run the file "nmake /nologo" and will fail
when such a file isn't found. On the other
hand, perl will now execute code such as "sys-
tem("c:/Program Files/MyApp/foo.exe", @args)"
correctly.

o The perl header files no longer suppress com-
mon warnings from the Microsoft Visual C++
compiler. This means that additional warnings
may now show up when compiling XS code.

o Borland C++ v5.5 is now a supported compiler
that can build Perl. However, the generated
binaries continue to be incompatible with
those generated by the other supported compil-
ers (GCC and Visual C++). [561]

o Duping socket handles with open(F, ">&MYSOCK")
now works under Windows 9x. [561]

o Current directory entries in %ENV are now cor-
rectly propagated to child processes. [561]

o New %ENV entries now propagate to subpro-
cesses. [561]

o Win32::GetCwd() correctly returns C:\ instead
of C: when at the drive root. Other bugs in
chdir() and Cwd::cwd() have also been fixed.
[561]

o The makefiles now default to the features
enabled in ActiveState ActivePerl (a popular
Win32 binary distribution). [561]

o HTML files will now be installed in
c:\perl\html instead of c:\perl\lib\pod\html

o REG_EXPAND_SZ keys are now allowed in registry
settings used by perl. [561]

o Can now send() from all threads, not just the
first one. [561]

o ExtUtils::MakeMaker now uses $ENV{LIB} to
search for libraries. [561]

o Less stack reserved per thread so that more
threads can run concurrently. (Still 16M per
thread.) [561]

o "File::Spec->tmpdir()" now prefers C:/temp
over /tmp (works better when perl is running
as service).

o Better UNC path handling under ithreads. [561]

o wait(), waitpid(), and backticks now return
the correct exit status under Windows 9x.
[561]

o A socket handle leak in accept() has been
fixed. [561]

New or Changed Diagnostics
Please see perldiag for more details.

o Ambiguous range in the transliteration operator (like
a-z-9) now gives a warning.

o chdir("") and chdir(undef) now give a deprecation
warning because they cause a possible unintentional
chdir to the home directory. Say chdir() if you
really mean that.

o Two new debugging options have been added: if you have
compiled your Perl with debugging, you can use the -DT
[561] and -DR options to trace tokenising and to add
reference counts to displaying variables, respec-
tively.

o The lexical warnings category "deprecated" is no
longer a sub-category of the "syntax" category. It is
now a top-level category in its own right.

o Unadorned dump() will now give a warning suggesting to
use explicit CORE::dump() if that's what really is
meant.

o The "Unrecognized escape" warning has been extended to
include "\8", "\9", and "\_". There is no need to
escape any of the "\w" characters.

o All regular expression compilation error messages are
now hopefully easier to understand both because the
error message now comes before the failed regex and
because the point of failure is now clearly marked by
a "<-- HERE" marker.

o Various I/O (and socket) functions like binmode(),
close(), and so forth now more consistently warn if
they are used illogically either on a yet unopened or
on an already closed filehandle (or socket).

o Using lstat() on a filehandle now gives a warning.
(It's a non-sensical thing to do.)

o The "-M" and "-m" options now warn if you didn't sup-
ply the module name.

o If you in "use" specify a required minimum version,
modules matching the name and but not defining a $VER-
SION will cause a fatal failure.

o Using negative offset for vec() in lvalue context is
now a warnable offense.

o Odd number of arguments to overload::constant now
elicits a warning.

o Odd number of elements in anonymous hash now elicits a
warning.

o The various "opened only for", "on closed", "never
opened" warnings drop the "main::" prefix for filehan-
dles in the "main" package, for example "STDIN"
instead of "main::STDIN".

o Subroutine prototypes are now checked more carefully,
you may get warnings for example if you have used non-
prototype characters.

o If an attempt to use a (non-blessed) reference as an
array index is made, a warning is given.

o "push @a;" and "unshift @a;" (with no values to push
or unshift) now give a warning. This may be a problem
for generated and evaled code.

o If you try to "pack" in perlfunc a number less than 0
or larger than 255 using the "C" format you will get
an optional warning. Similarly for the "c" format and
a number less than -128 or more than 127.

o pack "P" format now demands an explicit size.

o unpack "w" now warns of unterminated compressed inte-
gers.

o Warnings relating to the use of PerlIO have been
added.

o Certain regex modifiers such as "(?o)" make sense only
if applied to the entire regex. You will get an
optional warning if you try to do otherwise.

o Variable length lookbehind has not yet been imple-
mented, trying to use it will tell that.

o Using arrays or hashes as references (e.g.
"%foo->{bar}" has been deprecated for a while. Now
you will get an optional warning.

o Warnings relating to the use of the new restricted
hashes feature have been added.

o Self-ties of arrays and hashes are not supported and
fatal errors will happen even at an attempt to do so.

o Using "sort" in scalar context now issues an optional
warning. This didn't do anything useful, as the sort
was not performed.

o Using the /g modifier in split() is meaningless and
will cause a warning.

o Using splice() past the end of an array now causes a
warning.

o Malformed Unicode encodings (UTF-8 and UTF-16) cause a
lot of warnings, as does trying to use UTF-16 surro-
gates (which are unimplemented).

o Trying to use Unicode characters on an I/O stream
without marking the stream's encoding (using open() or
binmode()) will cause "Wide character" warnings.

o Use of v-strings in use/require causes a (backward)
portability warning.

o Warnings relating to the use interpreter threads and
their shared data have been added.

Changed Internals
o PerlIO is now the default.

o perlapi.pod (a companion to perlguts) now attempts to
document the internal API.

o You can now build a really minimal perl called microp-
erl. Building microperl does not require even running
Configure; "make -f Makefile.micro" should be enough.
Beware: microperl makes many assumptions, some of
which may be too bold; the resulting executable may
crash or otherwise misbehave in wondrous ways. For
careful hackers only.

o Added rsignal(), whichsig(), do_join(), op_clear,
op_null, ptr_table_clear(), ptr_table_free(),
sv_setref_uv(), and several UTF-8 interfaces to the
publicised API. For the full list of the available
APIs see perlapi.

o Made possible to propagate customised exceptions via
croak()ing.

o Now xsubs can have attributes just like subs. (Well,
at least the built-in attributes.)

o dTHR and djSP have been obsoleted; the former removed
(because it's a no-op) and the latter replaced with
dSP.

o PERL_OBJECT has been completely removed.

o The MAGIC constants (e.g. 'P') have been macrofied
(e.g. "PERL_MAGIC_TIED") for better source code read-
ability and maintainability.

o The regex compiler now maintains a structure that
identifies nodes in the compiled bytecode with the
corresponding syntactic features of the original regex
expression. The information is attached to the new
"offsets" member of the "struct regexp". See perlde-
bguts for more complete information.

o The C code has been made much more "gcc -Wall" clean.
Some warning messages still remain in some platforms,
so if you are compiling with gcc you may see some
warnings about dubious practices. The warnings are
being worked on.

o perly.c, sv.c, and sv.h have now been extensively com-
mented.

o Documentation on how to use the Perl source repository
has been added to Porting/repository.pod.

o There are now several profiling make targets.

Security Vulnerability Closed [561]
(This change was already made in 5.7.0 but bears repeating
here.) (5.7.0 came out before 5.6.1: the development
branch 5.7 released earlier than the maintenance branch
5.6)

A potential security vulnerability in the optional suid-
perl component of Perl was identified in August 2000.
suidperl is neither built nor installed by default. As of
November 2001 the only known vulnerable platform is Linux,
most likely all Linux distributions. CERT and various
vendors and distributors have been alerted about the vul-
nerability. See
http://www.cpan.org/src/5.0/sperl-2000-08-05/sperl-2000-08-05.txt
for more information.

The problem was caused by Perl trying to report a sus-
pected security exploit attempt using an external program,
/bin/mail. On Linux platforms the /bin/mail program had
an undocumented feature which when combined with suidperl
gave access to a root shell, resulting in a serious com-
promise instead of reporting the exploit attempt. If you
don't have /bin/mail, or if you have 'safe setuid
scripts', or if suidperl is not installed, you are safe.

The exploit attempt reporting feature has been completely
removed from Perl 5.8.0 (and the maintenance release
5.6.1, and it was removed also from all the Perl 5.7
releases), so that particular vulnerability isn't there
anymore. However, further security vulnerabilities are,
unfortunately, always possible. The suidperl functional-
ity is most probably going to be removed in Perl 5.10. In
any case, suidperl should only be used by security experts
who know exactly what they are doing and why they are
using suidperl instead of some other solution such as sudo
( see http://www.courtesan.com/sudo/ ).

New Tests
Several new tests have been added, especially for the lib
and ext subsections. There are now about 69 000 individ-
ual tests (spread over about 700 test scripts), in the
regression suite (5.6.1 has about 11 700 tests, in 258
test scripts) The exact numbers depend on the platform
and Perl configuration used. Many of the new tests are of
course introduced by the new modules, but still in general
Perl is now more thoroughly tested.

Because of the large number of tests, running the regres-
sion suite will take considerably longer time than it used
to: expect the suite to take up to 4-5 times longer to run
than in perl 5.6. On a really fast machine you can hope
to finish the suite in about 6-8 minutes (wallclock time).

The tests are now reported in a different order than in
earlier Perls. (This happens because the test scripts
from under t/lib have been moved to be closer to the
library/extension they are testing.)

Known Problems
The Compiler Suite Is Still Very Experimental

The compiler suite is slowly getting better but it contin-
ues to be highly experimental. Use in production environ-
ments is discouraged.

Localising Tied Arrays and Hashes Is Broken

local %tied_array;

doesn't work as one would expect: the old value is
restored incorrectly. This will be changed in a future
release, but we don't know yet what the new semantics will
exactly be. In any case, the change will break existing
code that relies on the current (ill-defined) semantics,
so just avoid doing this in general.

Building Extensions Can Fail Because Of Largefiles

Some extensions like mod_perl are known to have issues
with `largefiles', a change brought by Perl 5.6.0 in which
file offsets default to 64 bits wide, where supported.
Modules may fail to compile at all, or they may compile
and work incorrectly. Currently, there is no good solu-
tion for the problem, but Configure now provides appropri-
ate non-largefile ccflags, ldflags, libswanted, and libs
in the %Config hash (e.g., $Config{ccflags_nolargefiles})
so the extensions that are having problems can try config-
uring themselves without the largefileness. This is
admittedly not a clean solution, and the solution may not
even work at all. One potential failure is whether one
can (or, if one can, whether it's a good idea to) link
together at all binaries with different ideas about file
offsets; all this is platform-dependent.

Modifying $_ Inside for(..)

for (1..5) { $_++ }

works without complaint. It shouldn't. (You should be
able to modify only lvalue elements inside the loops.)
You can see the correct behaviour by replacing the 1..5
with 1, 2, 3, 4, 5.

mod_perl 1.26 Doesn't Build With Threaded Perl

Use mod_perl 1.27 or higher.

lib/ftmp-security tests warn 'system possibly insecure'

Don't panic. Read the 'make test' section of INSTALL
instead.

libwww-perl (LWP) fails base/date #51

Use libwww-perl 5.65 or later.

PDL failing some tests

Use PDL 2.3.4 or later.

Perl_get_sv

You may get errors like 'Undefined symbol "Perl_get_sv"'
or "can't resolve symbol 'Perl_get_sv'", or the symbol may
be "Perl_sv_2pv". This probably means that you are trying
to use an older shared Perl library (or extensions linked
with such) with Perl 5.8.0 executable. Perl used to have
such a subroutine, but that is no more the case. Check
your shared library path, and any shared Perl libraries in
those directories.

Sometimes this problem may also indicate a partial Perl
5.8.0 installation, see "Mac OS X dyld undefined symbols"
for an example and how to deal with it.

Self-tying Problems

Self-tying of arrays and hashes is broken in rather deep
and hard-to-fix ways. As a stop-gap measure to avoid peo-
ple from getting frustrated at the mysterious results
(core dumps, most often), it is forbidden for now (you
will get a fatal error even from an attempt).

A change to self-tying of globs has caused them to be
recursively referenced (see: "Two-Phased Garbage Collec-
tion" in perlobj). You will now need an explicit untie to
destroy a self-tied glob. This behaviour may be fixed at
a later date.

Self-tying of scalars and IO thingies works.

ext/threads/t/libc

If this test fails, it indicates that your libc (C
library) is not threadsafe. This particular test stress
tests the localtime() call to find out whether it is
threadsafe. See perlthrtut for more information.

Failure of Thread (5.005-style) tests

Note that support for 5.005-style threading is deprecated,
experimental and practically unsupported. In 5.10, it is
expected to be removed. You should migrate your code to
ithreads.

The following tests are known to fail due to fundamental
problems in the 5.005 threading implementation. These are
not new failures--Perl 5.005_0x has the same bugs, but
didn't have these tests.

../ext/B/t/xref.t 255 65280 14 12 85.71% 3-14
../ext/List/Util/t/first.t 255 65280 7 4 57.14% 2 5-7
../lib/English.t 2 512 54 2 3.70% 2-3
../lib/FileCache.t 5 1 20.00% 5
../lib/Filter/Simple/t/data.t 6 3 50.00% 1-3
../lib/Filter/Simple/t/filter_only. 9 3 33.33% 1-2 5
../lib/Math/BigInt/t/bare_mbf.t 1627 4 0.25% 8 11 1626-1627
../lib/Math/BigInt/t/bigfltpm.t 1629 4 0.25% 10 13 1628-
1629
../lib/Math/BigInt/t/sub_mbf.t 1633 4 0.24% 8 11 1632-1633
../lib/Math/BigInt/t/with_sub.t 1628 4 0.25% 9 12 1627-1628
../lib/Tie/File/t/31_autodefer.t 255 65280 65 32 49.23% 34-65
../lib/autouse.t 10 1 10.00% 4
op/flip.t 15 1 6.67% 15

These failures are unlikely to get fixed as 5.005-style
threads are considered fundamentally broken. (Basically
what happens is that competing threads can corrupt shared
global state, one good example being regular expression
engine's state.)

Timing problems

The following tests may fail intermittently because of
timing problems, for example if the system is heavily
loaded.

t/op/alarm.t
ext/Time/HiRes/HiRes.t
lib/Benchmark.t
lib/Memoize/t/expmod_t.t
lib/Memoize/t/speed.t

In case of failure please try running them manually, for
example

./perl -Ilib ext/Time/HiRes/HiRes.t

Tied/Magical Array/Hash Elements Do Not Autovivify

For normal arrays "$foo = \$bar[1]" will assign "undef" to
$bar[1] (assuming that it didn't exist before), but for
tied/magical arrays and hashes such autovivification does
not happen because there is currently no way to catch the
reference creation. The same problem affects slicing over
non-existent indices/keys of a tied/magical array/hash.

Unicode in package/class and subroutine names does not
work

One can have Unicode in identifier names, but not in pack-
age/class or subroutine names. While some limited func-
tionality towards this does exist as of Perl 5.8.0, that
is more accidental than designed; use of Unicode for the
said purposes is unsupported.

One reason of this unfinishedness is its (currently)
inherent unportability: since both package names and sub-
routine names may need to be mapped to file and directory
names, the Unicode capability of the filesystem becomes
important-- and there unfortunately aren't portable
answers.

Platform Specific Problems
AIX

o If using the AIX native make command, instead of just
"make" issue "make all". In some setups the former
has been known to spuriously also try to run "make
install". Alternatively, you may want to use GNU
make.

o In AIX 4.2, Perl extensions that use C++ functions
that use statics may have problems in that the statics
are not getting initialized. In newer AIX releases,
this has been solved by linking Perl with the libC_r
library, but unfortunately in AIX 4.2 the said library
has an obscure bug where the various functions related
to time (such as time() and gettimeofday()) return
broken values, and therefore in AIX 4.2 Perl is not
linked against libC_r.

o vac 5.0.0.0 May Produce Buggy Code For Perl

The AIX C compiler vac version 5.0.0.0 may produce
buggy code, resulting in a few random tests failing
when run as part of "make test", but when the failing
tests are run by hand, they succeed. We suggest
upgrading to at least vac version 5.0.1.0, that has
been known to compile Perl correctly. "lslpp -L|grep
vac.C" will tell you the vac version. See README.aix.

o If building threaded Perl, you may get compilation
warning from pp_sys.c:

"pp_sys.c", line 4651.39: 1506-280 (W) Function argument assignment between types "unsigned char*" and "const void*" is not allowed.

This is harmless; it is caused by the getnetbyaddr()
and getnetbyaddr_r() having slightly different types
for their first argument.

Alpha systems with old gccs fail several tests

If you see op/pack, op/pat, op/regexp, or ext/Storable
tests failing in a Linux/alpha or *BSD/Alpha, it's proba-
bly time to upgrade your gcc. gccs prior to 2.95.3 are
definitely not good enough, and gcc 3.1 may be even bet-
ter. (RedHat Linux/alpha with gcc 3.1 reported no prob-
lems, as did Linux 2.4.18 with gcc 2.95.4.) (In Tru64, it
is preferable to use the bundled C compiler.)

AmigaOS

Perl 5.8.0 doesn't build in AmigaOS. It broke at some
point during the ithreads work and we could not find Amiga
experts to unbreak the problems. Perl 5.6.1 still works
for AmigaOS (as does the 5.7.2 development release).

BeOS

The following tests fail on 5.8.0 Perl in BeOS Personal
5.03:

t/op/lfs............................FAILED at test 17
t/op/magic..........................FAILED at test 24
ext/Fcntl/t/syslfs..................FAILED at test 17
ext/File/Glob/t/basic...............FAILED at test 3
ext/POSIX/t/sigaction...............FAILED at test 13
ext/POSIX/t/waitpid.................FAILED at test 1

See perlbeos (README.beos) for more details.

Cygwin "unable to remap"

For example when building the Tk extension for Cygwin, you
may get an error message saying "unable to remap". This
is known problem with Cygwin, and a workaround is detailed
in here: http://sources.redhat.com/ml/cyg-
win/2001-12/msg00894.html

Cygwin ndbm tests fail on FAT

One can build but not install (or test the build of) the
NDBM_File on FAT filesystems. Installation (or build) on
NTFS works fine. If one attempts the test on a FAT
install (or build) the following failures are expected:

../ext/NDBM_File/ndbm.t 13 3328 71 59 83.10% 1-2 4 16-71
../ext/ODBM_File/odbm.t 255 65280 ?? ?? % ??
../lib/AnyDBM_File.t 2 512 12 2 16.67% 1 4
../lib/Memoize/t/errors.t 0 139 11 5 45.45% 7-11
../lib/Memoize/t/tie_ndbm.t 13 3328 4 4 100.00% 1-4
run/fresh_perl.t 97 1 1.03% 91

NDBM_File fails and ODBM_File just coredumps.

If you intend to run only on FAT (or if using AnyDBM_File
on FAT), run Configure with the -Ui_ndbm and -Ui_dbm
options to prevent NDBM_File and ODBM_File being built.

DJGPP Failures

t/op/stat............................FAILED at test 29
lib/File/Find/t/find.................FAILED at test 1
lib/File/Find/t/taint................FAILED at test 1
lib/h2xs.............................FAILED at test 15
lib/Pod/t/eol........................FAILED at test 1
lib/Test/Harness/t/strap-analyze.....FAILED at test 8
lib/Test/Harness/t/test-harness......FAILED at test 23
lib/Test/Simple/t/exit...............FAILED at test 1

The above failures are known as of 5.8.0 with native
builds with long filenames, but there are a few more if
running under dosemu because of limitations (and maybe
bugs) of dosemu:

t/comp/cpp...........................FAILED at test 3
t/op/inccode.........................(crash)

and a few lib/ExtUtils tests, and several hundred
Encode/t/Aliases.t failures that work fine with long file-
names. So you really might prefer native builds and long
filenames.

FreeBSD built with ithreads coredumps reading large direc-
tories

This is a known bug in FreeBSD 4.5's readdir_r(), it has
been fixed in FreeBSD 4.6 (see perlfreebsd
(README.freebsd)).

FreeBSD Failing locale Test 117 For ISO 8859-15 Locales

The ISO 8859-15 locales may fail the locale test 117 in
FreeBSD. This is caused by the characters \xFF (y with
diaeresis) and \xBE (Y with diaeresis) not behaving cor-
rectly when being matched case-insensitively. Apparently
this problem has been fixed in the latest FreeBSD
releases. (
http://www.freebsd.org/cgi/query-pr.cgi?pr=34308 )

IRIX fails ext/List/Util/t/shuffle.t or Digest::MD5

IRIX with MIPSpro 7.3.1.2m or 7.3.1.3m compiler may fail
the List::Util test ext/List/Util/t/shuffle.t by dumping
core. This seems to be a compiler error since if compiled
with gcc no core dump ensues, and no failures have been
seen on the said test on any other platform.

Similarly, building the Digest::MD5 extension has been
known to fail with "*** Termination code 139 (bu21)".

The cure is to drop optimization level (Configure -Dopti-
mize=-O2).

HP-UX lib/posix Subtest 9 Fails When LP64-Configured

If perl is configured with -Duse64bitall, the successful
result of the subtest 10 of lib/posix may arrive before
the successful result of the subtest 9, which confuses the
test harness so much that it thinks the subtest 9 failed.

Linux with glibc 2.2.5 fails t/op/int subtest #6 with
-Duse64bitint

This is a known bug in the glibc 2.2.5 with long long
integers. ( http://bugzilla.red-
hat.com/bugzilla/show_bug.cgi?id=65612 )

Linux With Sfio Fails op/misc Test 48

No known fix.

Mac OS X

Please remember to set your environment variable LC_ALL to
"C" (setenv LC_ALL C) before running "make test" to avoid
a lot of warnings about the broken locales of Mac OS X.

The following tests are known to fail in Mac OS X 10.1.5
because of buggy (old) implementations of Berkeley DB
included in Mac OS X:

Failed Test Stat Wstat Total Fail Failed List of Failed
-------------------------------------------------------------------------
../ext/DB_File/t/db-btree.t 0 11 ?? ?? % ??
../ext/DB_File/t/db-recno.t 149 3 2.01% 61 63 65

If you are building on a UFS partition, you will also
probably see t/op/stat.t subtest #9 fail. This is caused
by Darwin's UFS not supporting inode change time.

Also the ext/POSIX/t/posix.t subtest #10 fails but it is
skipped for now because the failure is Apple's fault, not
Perl's (blocked signals are lost).

If you Configure with ithreads, ext/threads/t/libc.t will
fail. Again, this is not Perl's fault-- the libc of Mac OS
X is not threadsafe (in this particular test, the local-
time() call is found to be threadunsafe.)

Mac OS X dyld undefined symbols

If after installing Perl 5.8.0 you are getting warnings
about missing symbols, for example

dyld: perl Undefined symbols
_perl_sv_2pv
_perl_get_sv

you probably have an old pre-Perl-5.8.0 installation (or
parts of one) in /Library/Perl (the undefined symbols used
to exist in pre-5.8.0 Perls). It seems that for some rea-
son "make install" doesn't always completely overwrite the
files in /Library/Perl. You can move the old Perl shared
library out of the way like this:

cd /Library/Perl/darwin/CORE
mv libperl.dylib libperlold.dylib

and then reissue "make install". Note that the above of
course is extremely disruptive for anything using the
/usr/local/bin/perl. If that doesn't help, you may have
to try removing all the .bundle files from beneath
/Library/Perl, and again "make install"-ing.

OS/2 Test Failures

The following tests are known to fail on OS/2 (for clarity
only the failures are shown, not the full error messages):

../lib/ExtUtils/t/Mkbootstrap.t 1 256 18 1 5.56% 8
../lib/ExtUtils/t/Packlist.t 1 256 34 1 2.94% 17
../lib/ExtUtils/t/basic.t 1 256 17 1 5.88% 14
lib/os2_process.t 2 512 227 2 0.88% 174 209
lib/os2_process_kid.t 227 2 0.88% 174 209
lib/rx_cmprt.t 255 65280 18 3 16.67% 16-18

op/sprintf tests 91, 129, and 130

The op/sprintf tests 91, 129, and 130 are known to fail on
some platforms. Examples include any platform using sfio,
and Compaq/Tandem's NonStop-UX.

Test 91 is known to fail on QNX6 (nto), because "sprintf
'%e',0" incorrectly produces 0.000000e+0 instead of
0.000000e+00.

For tests 129 and 130, the failing platforms do not comply
with the ANSI C Standard: lines 19ff on page 134 of ANSI
X3.159 1989, to be exact. (They produce something other
than "1" and "-1" when formatting 0.6 and -0.6 using the
printf format "%.0f"; most often, they produce "0" and
"-0".)

SCO

The socketpair tests are known to be unhappy in SCO
3.2v5.0.4:

ext/Socket/socketpair.t...............FAILED tests 15-45

Solaris 2.5

In case you are still using Solaris 2.5 (aka SunOS 5.5),
you may experience failures (the test core dumping) in
lib/locale.t. The suggested cure is to upgrade your
Solaris.

Solaris x86 Fails Tests With -Duse64bitint

The following tests are known to fail in Solaris x86 with
Perl configured to use 64 bit integers:

ext/Data/Dumper/t/dumper.............FAILED at test 268
ext/Devel/Peek/Peek..................FAILED at test 7

SUPER-UX (NEC SX)

The following tests are known to fail on SUPER-UX:

op/64bitint...........................FAILED tests 29-30, 32-33, 35-36
op/arith..............................FAILED tests 128-130
op/pack...............................FAILED tests 25-5625
op/pow................................
op/taint..............................# msgsnd failed
../ext/IO/lib/IO/t/io_poll............FAILED tests 3-4
../ext/IPC/SysV/ipcsysv...............FAILED tests 2, 5-6
../ext/IPC/SysV/t/msg.................FAILED tests 2, 4-6
../ext/Socket/socketpair..............FAILED tests 12
../lib/IPC/SysV.......................FAILED tests 2, 5-6
../lib/warnings.......................FAILED tests 115-116, 118-119

The op/pack failure ("Cannot compress negative numbers at
op/pack.t line 126") is serious but as of yet unsolved.
It points at some problems with the signedness handling of
the C compiler, as do the 64bitint, arith, and pow fail-
ures. Most of the rest point at problems with SysV IPC.

Term::ReadKey not working on Win32

Use Term::ReadKey 2.20 or later.

UNICOS/mk

o During Configure, the test

Guessing which symbols your C compiler and preprocessor define...

will probably fail with error messages like

CC-20 cc: ERROR File = try.c, Line = 3
The identifier "bad" is undefined.

bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
^

CC-65 cc: ERROR File = try.c, Line = 3
A semicolon is expected at this point.

This is caused by a bug in the awk utility of UNI-
COS/mk. You can ignore the error, but it does cause a
slight problem: you cannot fully benefit from the h2ph
utility (see h2ph) that can be used to convert C head-
ers to Perl libraries, mainly used to be able to
access from Perl the constants defined using C prepro-
cessor, cpp. Because of the above error, parts of the
converted headers will be invisible. Luckily, these
days the need for h2ph is rare.

o If building Perl with interpreter threads (ithreads),
the getgrent(), getgrnam(), and getgrgid() functions
cannot return the list of the group members due to a
bug in the multithreaded support of UNICOS/mk. What
this means is that in list context the functions will
return only three values, not four.

UTS

There are a few known test failures, see perluts
(README.uts).

VOS (Stratus)

When Perl is built using the native build process on VOS
Release 14.5.0 and GNU C++/GNU Tools 2.0.1, all attempted
tests either pass or result in TODO (ignored) failures.

VMS

There should be no reported test failures with a default
configuration, though there are a number of tests marked
TODO that point to areas needing further debugging and/or
porting work.

Win32

In multi-CPU boxes, there are some problems with the I/O
buffering: some output may appear twice.

XML::Parser not working

Use XML::Parser 2.31 or later.

z/OS (OS/390)

z/OS has rather many test failures but the situation is
actually much better than it was in 5.6.0; it's just that
so many new modules and tests have been added.

Failed Test Stat Wstat Total Fail Failed List of Failed
---------------------------------------------------------------------------
../ext/Data/Dumper/t/dumper.t 357 8 2.24% 311 314 325 327
331 333 337 339
../ext/IO/lib/IO/t/io_unix.t 5 4 80.00% 2-5
../ext/Storable/t/downgrade.t 12 3072 169 12 7.10% 14-15 46-47 78-79
110-111 150 161
../lib/ExtUtils/t/Constant.t 121 30976 48 48 100.00% 1-48
../lib/ExtUtils/t/Embed.t 9 9 100.00% 1-9
op/pat.t 922 7 0.76% 665 776 785 832-
834 845
op/sprintf.t 224 3 1.34% 98 100 136
op/tr.t 97 5 5.15% 63 71-74
uni/fold.t 780 6 0.77% 61 169 196 661
710-711

The failures in dumper.t and downgrade.t are problems in
the tests, those in io_unix and sprintf are problems in
the USS (UDP sockets and printf formats). The pat, tr,
and fold failures are genuine Perl problems caused by
EBCDIC (and in the pat and fold cases, combining that with
Unicode). The Constant and Embed are probably problems in
the tests (since they test Perl's ability to build exten-
sions, and that seems to be working reasonably well.)

Unicode Support on EBCDIC Still Spotty

Though mostly working, Unicode support still has problem
spots on EBCDIC platforms. One such known spot are the
"\p{}" and "\P{}" regular expression constructs for code
points less than 256: the "pP" are testing for Unicode
code points, not knowing about EBCDIC.

Seen In Perl 5.7 But Gone Now

"Time::Piece" (previously known as "Time::Object") was
removed because it was felt that it didn't have enough
value in it to be a core module. It is still a useful
module, though, and is available from the CPAN.

Perl 5.8 unfortunately does not build anymore on AmigaOS;
this broke accidentally at some point. Since there are
not that many Amiga developers available, we could not get
this fixed and tested in time for 5.8.0. Perl 5.6.1 still
works for AmigaOS (as does the 5.7.2 development release).

The "PerlIO::Scalar" and "PerlIO::Via" (capitalised) were
renamed as "PerlIO::scalar" and "PerlIO::via" (all lower-
case) just before 5.8.0. The main rationale was to have
all core PerlIO layers to have all lowercase names. The
"plugins" are named as usual, for example "Per-
lIO::via::QuotedPrint".

The "threads::shared::queue" and
"threads::shared::semaphore" were renamed as
"Thread::Queue" and "Thread::Semaphore" just before 5.8.0.
The main rationale was to have thread modules to obey nor-
mal naming, "Thread::" (the "threads" and
"threads::shared" themselves are more pragma-like, they
affect compile-time, so they stay lowercase).

Reporting Bugs
If you find what you think is a bug, you might check the
articles recently posted to the comp.lang.perl.misc news-
group and the perl bug database at http://bugs.perl.org/ .
There may also be information at http://www.perl.com/ ,
the Perl Home Page.

If you believe you have an unreported bug, please run the
perlbug program included with your release. Be sure to
trim your bug down to a tiny but sufficient test case.
Your bug report, along with the output of "perl -V", will
be sent off to perlbug@perl.org to be analysed by the Perl
porting team.

SEE ALSO
The Changes file for exhaustive details on what changed.

The INSTALL file for how to build Perl.

The README file for general stuff.

The Artistic and Copying files for copyright information.

HISTORY
Written by Jarkko Hietaniemi .

perl v5.8.8 2006-01-07 PERL58DELTA(1)

Interix / SUA

Hosted at SUA Community for Interix, SUA and SFU

Interix / SUA