=encoding utf8

=head1 NAME

perl5336delta - what is new for perl v5.33.6

=head1 DESCRIPTION

This document describes differences between the 5.33.5 release and the
5.33.6 release.

If you are upgrading from an earlier release such as 5.33.4, first read
L<perl5335delta>, which describes differences between 5.33.4 and 5.33.5.

=head1 Core Enhancements

=head2 C<qr/{,n}/> is now accepted

An empty lower bound is now accepted for regular expression quantifiers,
like C<{,3}>.

=head2 Blanks freely allowed within but adjacent to curly braces

(in double-quotish contexts and regular expression patterns)

This means you can write things like S<C<\x{ FFFC }>> if you like.  This
applies to all such constructs, namely C<\b{}>, C<\g{}>, C<\k{}>,
C<\N{}>, C<\o{}>, and C<\x{}>; as well as the regular expression
quantifier C<{I<m>,I<n>}>.  C<\p{}> and C<\P{}> retain their
already-existing, even looser, rules mandated by the Unicode standard
(see L<perluniprops/Properties accessible through \p{} and \P{}>).

This ability is in effect regardless of the presence of the C</x>
regular expression pattern modifier.

Additionally, the comma in a regular expression braced quantifier may
have blanks (tabs or spaces) before and/or after the comma, like
S<C<qr/a{ 5, 7 }/>>.

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<Carp> has been upgraded from version 1.51 to 1.52.

=item *

L<Compress::Raw::Bzip2> has been upgraded from version 2.096 to 2.100.

=item *

L<Compress::Raw::Zlib> has been upgraded from version 2.096 to 2.100.

=item *

L<DynaLoader> has been upgraded from version 1.49 to 1.50.

=item *

L<ExtUtils::MakeMaker> has been upgraded from version 7.56 to 7.58.

=item *

L<ExtUtils::Manifest> has been upgraded from version 1.72 to 1.73.

=item *

L<feature> has been upgraded from version 1.61 to 1.62.

Added the default enabled C<bareword_filehandles> feature.

=item *

L<GDBM_File> has been upgraded from version 1.18 to 1.19.

New functions and compatibility for newer versions of GDBM.
[L<GH #18435|https://github.com/Perl/perl5/pull/18435>]

=item *

L<IO> has been upgraded from version 1.44 to 1.45.

IO::Socket now stores error messages in C<$IO::Socket::errstr>, in
addition to in C<$@>.

=item *

IO-Compress has been upgraded from version 2.096 to 2.100.

=item *

libnet has been upgraded from version 3.12 to 3.13.

=item *

L<Module::CoreList> has been upgraded from version 5.20201220 to 5.20210120.

=item *

L<POSIX> has been upgraded from version 1.96 to 1.97.

POSIX::signbit() behaviour has been improved.
[L<GH #18441|https://github.com/Perl/perl5/pull/18441>]

Documentation for C<asctime> clarifies that the result is always in English.
(Use C<strftime> for a localized result.)

=item *

L<Socket> has been upgraded from version 2.030 to 2.031.

=item *

L<warnings> has been upgraded from version 1.49 to 1.50.

=item *

L<XS::APItest> has been upgraded from version 1.14 to 1.15.

=back

=head1 Documentation

=head2 New Documentation

=head3 L<perlgov>

This document describes the goals, scope, system, and rules for Perl's new
governance model.

Other pod files, most notably L<perlpolicy>, were amended to reflect
its adoption.

=head2 Changes to Existing Documentation

We have attempted to update the documentation to reflect the changes
listed in this document.  If you find any we have missed, open an issue
at L<https://github.com/Perl/perl5/issues>.

Additionally, the following selected changes have been made:

=head3 L<perlcommunity>

=over 4

=item *

The freenode IRC URL has been updated.

=back

=head3 L<perlfunc>

=over 4

=item *

The L<localtime|perlfunc/localtime> entry has been improved and now
also states that the result of the function is always in English.

=back

=head3 L<perlsyn>

=over 4

=item *

A new example shows how a lexical C<my> variable can be declared
during the initialization of a C<for> loop.

=back

=head1 Diagnostics

The following additions or changes have been made to diagnostic output,
including warnings and fatal error messages.  For the complete list of
diagnostic messages, see L<perldiag>.

=head2 New Diagnostics

=head3 New Errors

=over 4

=item *

L<Bareword filehandle "%s" not allowed under 'no feature "bareword_filehandles"'|perldiag/"Bareword filehandle "%s" not allowed under 'no feature "bareword_filehandles"'">

This accompanies the new L<bareword_filehandles|feature/"The 'bareword_filehandles' feature."> feature.

=back

=head2 Changes to Existing Diagnostics

=over 4

=item *

L<Too few arguments for subroutine '%s' (got %d; expected %d)|perldiag/"Too few arguments for subroutine '%s' (got %d; expected %d)">

Subroutine argument-count mismatch errors now include the number of
given and expected arguments.

=item *

L<Too many arguments for subroutine '%s' (got %d; expected %d)|perldiag/"Too many arguments for subroutine '%s' (got %d; expected %d)">

Subroutine argument-count mismatch errors now include the number of
given and expected arguments.

=item *

L<Lost precision when %s %f by 1|perldiag/"Lost precision when %s %f by 1">

This warning was only issued for positive too-large values when 
incrementing, and only for negative ones when decrementing.
It is now issued for both positive or negative too-large values.
[L<GH #18333|https://github.com/Perl/perl5/issues/18333>]

=back

=head1 Configuration and Compilation

=over 4

=item * Configure

A new probe checks for buggy libc implementations of the C<gcvt>/C<qgcvt>
functions.
[L<GH #18170|https://github.com/Perl/perl5/issues/18170>]

=back

=head1 Testing

Tests were added and changed to reflect the other additions and
changes in this release.  Furthermore, these significant changes were
made:

=over 4

=item *

F<t/re/opt.t> was added, providing a test harness for regexp optimization.
[L<GH #18213|https://github.com/Perl/perl5/pull/18213>]

=item *

A workaround for CPAN distributions needing dot in C<@INC> has been removed
[L<GH #18394|https://github.com/Perl/perl5/pull/18394>].
All distributions that previously required the workaround have now been
adapted.

=back

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item Mac OS X

A number of system libraries no longer exist as actual files on Big Sur,
even though C<dlopen> will pretend they do, so now we fall back to C<dlopen>
if a library file can not be found.
[L<GH #18407|https://github.com/Perl/perl5/issues/18407>]

=item MS Windows

perl can now be built with C<USE_QUADMATH> on MS Windows using
(32-bit and 64-bit) mingw-w64 ports of gcc.
[L<GH #18465|https://github.com/Perl/perl5/pull/18465>]

The F<pl2bat.pl> utility now needs to C<use ExtUtils::PL2Bat>. This could
cause failures in parallel builds.

=back

=head1 Selected Bug Fixes

=over 4

=item *

Skip trying to constant fold an incomplete op tree
[L<GH #18380|https://github.com/Perl/perl5/issues/18380>]

Constant folding of chained comparison op trees could fail under certain
conditions, causing perl to crash. As a quick fix, constant folding is
now skipped for such op trees. This also addresses
[L<GH #17917|https://github.com/Perl/perl5/issues/17917>].

=item *

%g formatting broken on Ubuntu-18.04, NVSIZE == 8
[L<GH #18170|https://github.com/Perl/perl5/issues/18170>]

Buggy libc implementations of the C<gcvt> and C<qgcvt> functions
caused C<(s)printf> to incorrectly truncate C<%g> formatted numbers.
A new Configure probe now checks for this, with the result that the libc
C<sprintf> will be used in place of C<gcvt> and C<qgcvt>.

Tests added as part of this fix also revealed related problems in
some Windows builds. The makefiles for MINGW builds on Windows have
thus been adjusted to use USE_MINGW_ANSI_STDIO by default, ensuring
that they also provide correct C<(s)printf> formatting of numbers.

=item *

op.c: croak on "my $_" when "use utf8" is in effect
[L<GH #18449|https://github.com/Perl/perl5/issues/18449>]

The lexical topic feature experiment was removed in Perl v5.24 and
declaring C<my $_> became a compile time error. However, it was previously
still possible to make this declaration if C<use utf8> was in effect.

=item *

regexec.c: Fix assertion failure
[L<GH #18451|https://github.com/Perl/perl5/issues/18451>]

Fuzzing triggered an assertion failure in the regexp engine when too many
characters were copied into a buffer.

=back

=head1 Acknowledgements

Perl 5.33.6 represents approximately 4 weeks of development since Perl
5.33.5 and contains approximately 96,000 lines of changes across 450 files
from 26 authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 85,000 lines of changes to 320 .pm, .t, .c and .h files.

Perl continues to flourish into its fourth decade thanks to a vibrant
community of users and developers. The following people are known to have
contributed the improvements that became Perl 5.33.6:

Branislav Zahradník, Chris 'BinGOs' Williams, Craig A. Berry, Dan Book,
Daniel Böhmer, Daniel Laügt, Felipe Gasper, Hugo van der Sanden, James E
Keenan, Kang-min Liu, Karen Etheridge, Karl Williamson, Leon Timmermans, Max
Maischein, Michael G Schwern, Paul Evans, Ricardo Signes, Richard Leach,
Sawyer X, Sergey Poznyakoff, Sisyphus, Steve Hay, TAKAI Kousuke, Tomasz
Konojacki, Tom Hukins, Tony Cook.

The list above is almost certainly incomplete as it is automatically
generated from version control history. In particular, it does not include
the names of the (very much appreciated) contributors who reported issues to
the Perl bug tracker.

Many of the changes included in this version originated in the CPAN modules
included in Perl's core. We're grateful to the entire CPAN community for
helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please
see the F<AUTHORS> file in the Perl source distribution.

=head1 Reporting Bugs

If you find what you think is a bug, you might check the perl bug database
at L<https://github.com/Perl/perl5/issues>.  There may also be information at
L<http://www.perl.org/>, the Perl Home Page.

If you believe you have an unreported bug, please open an issue at
L<https://github.com/Perl/perl5/issues>.  Be sure to trim your bug down to a
tiny but sufficient test case.

If the bug you are reporting has security implications which make it
inappropriate to send to a public issue tracker, then see
L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
for details of how to report the issue.

=head1 Give Thanks

If you wish to thank the Perl 5 Porters for the work we had done in Perl 5,
you can do so by running the C<perlthanks> program:

    perlthanks

This will send an email to the Perl 5 Porters list with your show of thanks.

=head1 SEE ALSO

The F<Changes> file for an explanation of how to view exhaustive details on
what changed.

The F<INSTALL> file for how to build Perl.

The F<README> file for general stuff.

The F<Artistic> and F<Copying> files for copyright information.

=cut