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NAME
perldelta - 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 mainte-
nance 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 reading 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 configuration because without it
many new features of Perl 5.8 cannot be used. In other words: you just
have to recompile your modules containing XS code, sorry about that.

In future releases of Perl, non-PerlIO aware XS modules may become com-
pletely 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 malloc. Finally,
other applications than Perl (such as mod_perl) tend to prefer the sys-
tem malloc. Such platforms 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 emulated interface. This
change will probably break backward compatibility with compiled mod-
ules. 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 particu-
lar, however, 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 stati-
cally built in. This may or may not be a problem 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 internal floating
point format on OpenVMS Alpha, potentially breaking binary compatibil-
ity with external libraries or existing data. G_FLOAT is still avail-
able as a configuration 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 charac-
ters based on the Unicode numbering.

In general, scripts are more inclusive, but not universally so. For
example, while the script "Latin" includes all the Latin characters and
their various diacritic-adorned versions, it does not include the
various punctuation 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" pre-
fix 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 con-
flict, you can omit the "In" from the block name (e.g. "\p{BraillePat-
terns}"), 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 double (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 forbidden.

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

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 use-
fulness. 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 impor-
tantly) 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 dep-
recated. Its semantics were never that clear and its
implementation even less so. If you have used that feature to dis-
allow all but fully qualified 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 com-
pletely 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" "discipline" was the inverse of
":crlf". Turning off "clrfness" 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 formally defined
as being equivalent to binmode(FH) - which is in turn defined as
doing whatever is necessary 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 lay-
ers (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
implemented 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 implementation, 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 deprecated and
expected to be removed in Perl 5.10. Multithreaded 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 simi-
lar 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 better at compile-time for
invalid syntax. An optional warning is generated ("Illegal charac-
ter in prototype...") but this may be upgraded to a fatal error in
a future release.

o The "exec LIST" and "system LIST" operations now produce 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 regu-
lar expressions should work now, Unicode in tr/// should work now, Uni-
code in I/O should work now. See perluniintro for introduction and
perlunicode for details.

o The Unicode Character Database coming with Perl has been upgraded
to Unicode 3.2.0. For more information, see http://www.uni-
code.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 subdirectory. The most notable omission, for space
considerations, is the Unihan database.

o The properties \p{Blank} and \p{SpacePerl} have been added. "Blank"
is like C isblank(), that is, it contains only "horizontal whites-
pace" (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 addi-
tional information on changes with Unicode properties.

PerlIO is Now The Default

o IO is now by default done via PerlIO rather than system'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-implementation 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 internal 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 perlunicode, utf8, and http://www.uni-
code.org/unicode/reports/tr16/ for more information. In future
releases this naming may change. See perluniintro for more infor-
mation about UTF-8.

o If your environment variables (LC_ALL, LC_CTYPE, LANG) look like
you want to use UTF-8 (any of the 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 explic-
itly open() or binmode() with ":bytes" (see "open" in perlfunc and
"binmode" in perlfunc), or you can just use "binmode(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 File-
Handle' or other module via

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

That is a literal undef, not an undefined value.

ithreads

The new interpreter threads ("ithreads" for short) implementation 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 neces-
sary and detectable reentrant libc interfaces.

Restricted Hashes

A restricted hash is restricted to a certain set of keys, no keys out-
side 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 inopportune 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 signals no longer
interrupt Perl instantly. Perl will now first finish whatever it was
doing, like finishing an internal operation (like sort()) or an exter-
nal operation (like an I/O operation), and only then look at any
arrived signals (and before starting the next operation). No more cor-
rupt 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 under-
standing 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 deficien-
cies. This results hopefully in more accurate numbers.

Perl now tries internally to use integer values in numeric conversions
and basic arithmetics (+ - * /) if the arguments are integers, and
tries also to keep the results stored internally as integers. This
change leads to often slightly faster and always less lossy arith-
metics. (Previously 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 matter what. The
behavior in earlier versions of perl 5 was that arrays would interpo-
late 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\@exam-
ple.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 downgraded 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 byteorder 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 plat-
forms.)

Also, $Config{byteorder} is now computed dynamically--this is more
robust with "fat binaries" where an executable image contains bina-
ries 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 sub-
routine 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 consid-
ered deprecated, and possibly removed/changed in future releases.)

o chomp() and chop() are now overridable. Note, however, that their
prototype (as given by "prototype("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 per-
lembed.

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 situations, 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 context. How-
ever, 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 UTF8.

o my __PACKAGE__ $obj now works. [561]

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

o printf() and sprintf() now support parameter reordering 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 internation-
alised 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 create references
(useful for example if you want to emulate 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 substitute 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 contain 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 <FILEHANDLE> angle bracket operator.

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

o Use of the "/c" match modifier without an accompanying "/g" modi-
fier elicits a new warning: "Use of /c modifier 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 whatever 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 main-
tained by Arthur Bergman, allows a class to define attribute han-
dlers.

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 handlers. Handlers
can be specific to type (SCALAR, ARRAY, HASH, or CODE), or specific
to the exact compilation 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 customisable. 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 backends).

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 main-
tained by Paul Marquess, has been added. It is primarily used by
"h2xs" to enhance portability of XS modules between different ver-
sions 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 pos-
sibilities 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 PerlIO::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 subrou-
tines, 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 serial-
isation 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 utilities 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_brack-
eted(), extract_quotelike(), extract_codeblock(), extract_vari-
able(), extract_tagged(), extract_multiple(), gen_delimited_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 storing hash ref-
erences (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 Unicode Character
Database. See Unicode::UCD.

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

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

o "XS::APItest", by Tim Jenness, is a test extension that exercises
XS APIs. Currently only "printf()" is tested: how to output vari-
ous 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 study-
ing 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 podla-
tors 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 standard 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 infamous performance
hit by saying

use English '-no_match_vars';

(Assuming, of course, that you don't need the troublesome 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 backported 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 warn-
ings 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 ExtU-
tils::Constant). This means that they will be more robust and
hopefully faster.

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

o File::Find now has pre- and post-processing callbacks. It also
correctly changes directories when chasing symbolic links. Call-
backs (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 descriptors.

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, Reuse-
Addr. For clarity, you may want to prefer ReuseAddr.

o IO::Socket::INET now supports a value of zero for "LocalPort" (usu-
ally 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 avail-
able 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 con-
nectivity, or sympathetic firewalls. You can set the environment
variable PERL_TEST_Net_Ping to "1" (one) before running 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 handlers 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 missing because of
lack of support for files with "holes". A workaround for the prob-
lem 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 suc-
cessfully logged.

o The Test module has been significantly enhanced.

o Time::Local::timelocal() does not handle fractional seconds any-
more. The rationale is that neither does localtime(), and timelo-
cal() and localtime() are supposed 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 encodings 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 dif-
ferent versions of Perl.

o "h2xs" uses the new ExtUtils::Constant module which will affect
newly created extensions that define constants. 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 numbers even for integer con-
stants), and slightly faster, you might want to consider regenerat-
ing 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, com-
mand 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 conversion 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" utility.)

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 standard 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 plat-
forms. [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 applications, 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 conflict with
perltoot in filesystems restricted to "8.3" names).

o perluniintro is an introduction to using Unicode in Perl. (perlu-
nicode 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 following 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 Chi-
nese) 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 module.

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 gener-
ates 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 lit-
tle 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 triv-
ial, 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 quicksort'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 hap-
pen 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 com-
pletely 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 rescued at the last moment because it
is faster than mergesort on certain inputs and platforms. For
example, 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 number of distinct elements. The
quicksort divide and conquer strategy works well on platforms with
relatively 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 imple-
mentation 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://burtleburtle.net/bob/hash/doobs.html ). This algorithm is
reasonably 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 perl-
bench, 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 inte-
gers even on non-64-bit platforms.

o Policy.sh policy change: if you are reusing a Policy.sh file (see
INSTALL) and you use Configure -Dprefix=/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, otherlibdirs, is avail-
able. It can be used for example for vendor add-ons without dis-
turbing 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 automatic 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 differ-
ent operating system release than is running, it now gives a
clearly visible 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 including 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{archname} (also known as $^O)
anymore. Instead, if you explicitly choose not to use perlio (Con-
figure 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 parame-
ter "-Dafsroot=/some/where/else".

o APPLLIB_EXP, a lesser-known configuration-time definition, 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_ver-
sion_major db_version_minor db_version_patch)} from Perl and as
"DB_VERSION_MAJOR_CFG DB_VERSION_MINOR_CFG DB_VERSION_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, config.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 /tmp/perl/build/directory
cd /tmp/perl/build/directory
sh /path/to/perl/source/Configure -Dmksymlinks ...

This will create in /tmp/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 /tmp/perl/build/direc-
tory. [561]

o For Perl developers, several new make targets for profiling 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 target called "perl.gprof"
for generating a gprofiled Perl executable.

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

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

o Guidelines of how to construct minimal Perl installations have been
added to INSTALL.

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

Note that the 5.005 threads are unsupported and deprecated: 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 stringi-
fying floating-point numbers is now more picky about using sprintf
%.*g rules for the conversion. Some platforms that used to use
gcvt may now resort to the slower sprintf.

o The obsolete method of making a special (e.g., debugging) 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 "Supported Plat-
forms" 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 synchro-
nised) [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 spe-
cific ones) have been merged back to the main distribution.

o NetWare from Novell is now supported. See perlnetware.

o NonStop-UX is now supported. [561]

o NEC SUPER-UX is now supported.

o All the OpenBSD specific patches (except for the installation spe-
cific 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
considered to be "working" with Perl ithreads, keep in mind the
possible non-preemptability of the underlying thread implementa-
tion.

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

o The Amdahl UTS UNIX mainframe platform is now supported. [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, how-
ever, 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::Function::Names.

o caller() could cause core dumps in certain situations. Carp was
sometimes affected by this problem. In particular, 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 number 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 correctly to the socket if RemotePort is set. [561]

o The debugger (perl5db.pl) has been modified to present a more con-
sistent commands interface, via (CommandSet=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 redefinition of
dl_error() when statically building extensions 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 subroutines 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 correctly 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 unlocalised 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 man-
dated by POSIX.

o Some versions of glibc have a broken modfl(). This affects builds
with "-Duselongdouble". This version of Perl detects this broken-
ness 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 eliminated to be
more compatible with 5.005. Infinity is now recognised as a num-
ber. [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 sibling blocks
resulted in bogus warnings about "redeclaration" of the variables.
The problem has been corrected. [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 argu-
ments 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 char-
acters, 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 wantarray context
(they were accidentally using the context of the sort() itself).
The comparison block is now run in scalar context, and the argu-
ments 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 whites-
pace (currently, the space and the tab).

o The tainting behaviour of sprintf() has been rationalized. 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 pessimised 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 situations. 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 cor-
rected. [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 cor-
rectly 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 Unicode 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 warn-
ing.

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

o Concatenation with the "." operator or via variable inter-
polation, "eq", "substr", "reverse", "quotemeta", the "x"
operator, substitution with "s///", single-quoted UTF8,
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, leading to spuri-
ous warnings. This has been corrected. [561]

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

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

o The Perl parser has been stress tested using both random 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; accidental 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 sockaddrlen when
using accept(), recvfrom() (in Perl: recv()), getpeer-
name(), and getsockname().

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 pack-
ages collection, or http://www.gnu.org/software/pth/), and Config-
ure 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 $Con-
fig{osvers}. Allow compiling with gcc (previously explicitly for-
bidden). 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 MULTI-
PLICITY (see INSTALL); now works with Perl's malloc.

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

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 func-
tionality 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 improve-
ment 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 itera-
tions 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 there-
fore 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 invo-
cations 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 con-
trol the visibility of windows created by child processes.
See Win32 for details.

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

o The behavior of system() with multiple arguments has been
rationalized. Each unquoted argument will be automatically
quoted to protect whitespace, and any existing whitespace
in the arguments will be preserved. This improves the
portability of system(@args) by avoiding the need for Win-
dows "cmd" shell specific 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, "system("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 "system("c:/Program
Files/MyApp/foo.exe", @args)" correctly.

o The perl header files no longer suppress common 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
compilers (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 correctly propa-
gated to child processes. [561]

o New %ENV entries now propagate to subprocesses. [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 distribu-
tion). [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 vari-
ables, respectively.

o The lexical warnings category "deprecated" is no longer a sub-cate-
gory 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 supply the module
name.

o If you in "use" specify a required minimum version, modules match-
ing the name and but not defining a $VERSION 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 warn-
ing.

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 filehandles 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 integers.

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 implemented, 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 warn-
ings, ad doestrying to use UTF-16 surrogates (which are unimple-
mented).

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 microperl. Building
microperl does not require even running Configure; "make -f Make-
file.micro" should be enough. Beware: microperl makes many assump-
tions, 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_ta-
ble_clear(), ptr_table_free(), sv_setref_uv(), and several UTF-8
interfaces to the publicised API. For the full list of the avail-
able 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 readability and maintain-
ability.

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 perldebguts
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 commented.

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 ear-
lier than the maintenance branch 5.6)

A potential security vulnerability in the optional suidperl 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 vari-
ous vendors and distributors have been alerted about the vulnerability.
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 suspected security
exploit attempt using an external program, /bin/mail. On Linux plat-
forms the /bin/mail program had an undocumented feature which when com-
bined with suidperl gave access to a root shell, resulting in a serious
compromise 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, unfortu-
nately, always possible. The suidperl functionality 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 sub-
sections. There are now about 69 000 individual 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 plat-
form 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 regression 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 (wall-
clock 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 continues to be
highly experimental. Use in production environments is discouraged.

Localising Tied Arrays and Hashes Is Broken

local %tied_array;

doesn't work as one would expect: the old value is restored incor-
rectly. 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 `large-
files', 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
solution for the problem, but Configure now provides appropriate 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 configuring 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 differ-
ent 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 installa-
tion, 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 people from getting frus-
trated at the mysterious results (core dumps, most often), it is for-
bidden 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 ref-
erenced (see: "Two-Phased Garbage Collection" 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 informa-
tion.

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 com-
peting 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 slic-
ing 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 package/class or
subroutine names. While some limited functionality 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 unporta-
bility: since both package names and subroutine 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 getnet-
byaddr_r() having slightly different types for their first argu-
ment.

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 probably time to upgrade your gcc.
gccs prior to 2.95.3 are definitely not good enough, and gcc 3.1 may be
even better. (RedHat Linux/alpha with gcc 3.1 reported no problems, 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 prob-
lems. Perl 5.6.1 still works for AmigaOS (as does the the 5.7.2 devel-
opment 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.red-
hat.com/ml/cygwin/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 filenames. So you really might pre-
fer native builds and long filenames.

FreeBSD built with ithreads coredumps reading large directories

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 correctly when being matched case-insensi-
tively. 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 -Doptimize=-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.redhat.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 sup-
porting 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 localtime() call is found to be threadun-
safe.)

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 reason "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 plat-
forms. 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" incor-
rectly 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 expe-
rience 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 config-
ured 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 prob-
lems with the signedness handling of the C compiler, as do the
64bitint, arith, and pow failures. 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 UNICOS/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 headers to Perl libraries, mainly used to be able to
access from Perl the constants defined using C preprocessor, 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 get-
grent(), 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 func-
tions 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 prob-
lems 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 extensions, 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{}" regu-
lar 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 devel-
opers 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 the 5.7.2
development release).

The "PerlIO::Scalar" and "PerlIO::Via" (capitalised) were renamed as
"PerlIO::scalar" and "PerlIO::via" (all lowercase) just before 5.8.0.
The main rationale was to have all core PerlIO layers to have all low-
ercase 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 normal 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 newsgroup 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 pro-
gram 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 <jhi@iki.fi>.