=encoding utf8

=head1 NAME

perl5316delta - what is new for perl v5.31.6

=head1 DESCRIPTION

This document describes differences between the 5.31.5 release and the 5.31.6
release.

If you are upgrading from an earlier release such as 5.31.4, first read
L<perl5315delta>, which describes differences between 5.31.4 and 5.31.5.

=head1 Core Enhancements

=head2 Alpha assertions are no longer experimental

See L<perlre/(*pla:pattern)>, L<perlre/(*plb:pattern)>,
L<perlre/(*nla:pattern)>>, and L<perlre/(*nlb:pattern)>.
Use of these no longer generates a warning; existing code that disables
the warning category C<experimental::script_run> will continue to work
without any changes needed.  Enabling the category has no effect.

=head2 Script runs are no longer experimental

See L<perlre/Script Runs>.  Use of these no longer generates a warning;
existing code that disables the warning category
C<experimental::alpha_assertions> will continue to work without any
changes needed.  Enabling the category has no effect.

=head2 Feature checks are now faster

Previously feature checks in the parser required a hash lookup when
features we set outside of a feature bundle, this has been optimized
to a bit mask check.  [#17229]

=head2 Perl is now developed on Github

Perl is now developed on Github, you can find us at
L<https://github.com/Perl/perl5>.

Non-security bugs should now be reported via Github.

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<B::Deparse> has been upgraded from version 1.50 to 1.51.

=item *

L<Compress::Raw::Bzip2> has been upgraded from version 2.087 to 2.090.

=item *

L<Compress::Raw::Zlib> has been upgraded from version 2.087 to 2.090.

=item *

L<Devel::PPPort> has been upgraded from version 3.54 to 3.55.

=item *

L<DynaLoader> has been upgraded from version 1.45 to 1.46.

=item *

L<feature> has been upgraded from version 1.55 to 1.56.

=item *

L<IO::Compress::Base> has been upgraded from version 2.087 to 2.090.

=item *

L<Math::BigInt> has been upgraded from version 1.999817_01 to 1.999818.

=item *

L<Module::CoreList> has been upgraded from version 5.20191020 to 5.20191120.

=item *

L<Module::Load::Conditional> has been upgraded from version 0.68 to 0.70.

=item *

L<mro> has been upgraded from version 1.22 to 1.23.

=item *

L<perlfaq> has been upgraded from version 5.20190126 to 5.20191102.

=item *

L<Pod::Simple> has been upgraded from version 3.39 to 3.40.

=item *

L<POSIX> has been upgraded from version 1.89 to 1.90.

=item *

L<Scalar::Util> has been upgraded from version 1.52 to 1.53.

=item *

L<Sys::Syslog> has been upgraded from version 0.35 to 0.36.

=item *

L<Test::Simple> has been upgraded from version 1.302168 to 1.302169.

=item *

L<Tie::StdHandle> has been upgraded from version 4.5 to 4.6.

=item *

L<Unicode::UCD> has been upgraded from version 0.73 to 0.74.

=item *

L<Win32API::File> has been upgraded from version 0.1203 to 0.1203_01.

=back

=head1 Utility Changes

=head2 L<streamzip>

=over 4

=item *

This is a new utility, included as part of an
L<IO::Compress::Base> upgrade.

L<streamzip> creates a zip file from stdin. The program will read data
from stdin, compress it into a zip container and, by default, write a
streamed zip file to stdout.

=back

=head1 Configuration and Compilation

=over 4

=item *

F<Configure> now correctly handles gcc-10. Previously it was interpreting it
as gcc-1 and turned on C<-fpcc-struct-return>.

=back

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item Windows

The configuration for C<ccflags> and C<optimize> are now separate, as
with POSIX platforms.  [#17156]

=back

=head1 Internal Changes

=over 4

=item *

The lexer (C<Perl_yylex()> in F<toke.c>) was previously a single 4100-line
function, relying heavily on C<goto> and a lot of widely-scoped local variables
to do its work. It has now been pulled apart into a few dozen smaller static
functions; the largest remaining chunk (C<yyl_word_or_keyword()>) is a little
over 900 lines, and consists of a single C<switch> statement, all of whose
C<case> groups are independent. This should be much easier to understand and
maintain.

=item *

The OS-level signal handlers and type (Sighandler_t) used by the perl core
were declared as having three parameters, but the OS was always told to
call them with one argument. This has been fixed by declaring them to have
one parameter. See the merge commit C<v5.31.5-346-g116e19abbf> for full
details.

=item *

The code that handles C<tr///> has been extensively revised, fixing
various bugs, especially when the source and/or replacement strings
contain characters whose code points are above 255.  Some of the bugs
were undocumented, one being that under some circumstances (but not all)
with C</s>, the squeezing was done based on the source, rather than the
replacement.  A documented bug that got fixed was [perl RT #125493].

=item *

A new macro for XS writers dealing with UTF-8-encoded Unicode strings
has been created L<perlapi/C<UTF8_CHK_SKIP>> that is safer in the face
of malformed UTF-8 input than L<perlapi/C<UTF8_SKIP>> (but not as safe
as L<perlapi/C<UTF8_SAFE_SKIP>>).  It won't read past a NUL character.
It has been backported in L<Devel::PPPort> 3.55 and later.

=back

=head1 Selected Bug Fixes

=over 4

=item *

printf() or sprintf() with the C<%n> format could cause a panic on
debugging builds, or report an incorrectly cached length value when
producing C<SVfUTF8> flagged strings. [#17221]

=item *

The tokenizer has been extensively refactored. [#17241][#17189]

=item *

C<use strict "subs"> is now enforced for bareword constants optimized
into a C<multiconcat> operator.  [#17254]

=item *

A memory leak in regular expression patterns has been fixed [#17218].

=back

=head1 Acknowledgements

Perl 5.31.6 represents approximately 4 weeks of development since Perl
5.31.5 and contains approximately 43,000 lines of changes across 490 files
from 31 authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 35,000 lines of changes to 300 .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 5.31.6:

Aaron Crane, Chad Granum, Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn
Ilmari Mannsåker, Dan Book, Dave Cross, David Mitchell, E. Choroba, Graham
Knop, Hauke D, Ichinose Shogo, James E Keenan, Karen Etheridge, Karl
Williamson, Matt Turner, Max Maischein, Nicholas Clark, Nicolas R., Pali,
Paul Evans, Petr Písař, Richard Leach, Sergey Aleynikov, Steve Hay, Steve
Peters, Todd Rinaldo, Tomasz Konojacki, Tom Hukins, Tony Cook, Yves Orton.

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 run the L<perlbug> program
included with your release.  Be sure to trim your bug down to a tiny but
sufficient test case.  Your bug report, along with the output of C<perl -V>,
will be sent off to perlbug@perl.org to be analysed by the Perl porting team.

If the bug you are reporting has security implications which make it
inappropriate to send to a publicly archived mailing list, 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
