=encoding utf8

=head1 NAME

perl5315delta - what is new for perl v5.31.5

=head1 DESCRIPTION

This document describes differences between the 5.31.4 release and the 5.31.5
release.

If you are upgrading from an earlier release such as 5.31.3, first read
L<perl5314delta>, which describes differences between 5.31.3 and 5.31.4.

=head1 Incompatible Changes

=head2 Modifiable variables are no longer permitted in constants

Code like:

    my $var;
    $sub = sub () { $var };

where C<$var> is referenced elsewhere in some sort of modifiable context now
produces an exception when the sub is defined.

This error can be avoided by adding a return to the sub definition:

    $sub = sub () { return $var };

This has been deprecated since Perl 5.22.

L<[perl #131138]|https://rt.perl.org/Ticket/Display.html?id=131138>.

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<B> has been upgraded from version 1.76 to 1.77.

=item *

L<B::Deparse> has been upgraded from version 1.49 to 1.50.

=item *

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

=item *

L<Digest::MD5> has been upgraded from version 2.55 to 2.55_01.

=item *

L<Dumpvalue> has been upgraded from version 1.18 to 1.21.

Previously, when dumping elements of an array and encountering an undefined
value, the string printed would have been C<empty array>.  This has been
changed to what was apparently originally intended:  C<empty slot>.

=item *

L<ExtUtils::CBuilder> has been upgraded from version 0.280232 to 0.280233.

=item *

L<Math::BigInt> has been upgraded from version 1.999816 to 1.999817_01.

=item *

L<Math::BigInt::FastCalc> has been upgraded from version 0.5008 to 0.5009.

=item *

L<Module::CoreList> has been upgraded from version 5.20190920 to 5.20191020.

=item *

L<Safe> has been upgraded from version 2.40 to 2.41.

=item *

L<threads> has been upgraded from version 2.22 to 2.23.

=item *

L<Time::HiRes> has been upgraded from version 1.9763 to 1.9764.

=item *

L<XS::APItest> has been upgraded from version 1.03 to 1.04.

=back

=head1 Documentation

=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, send email to
L<perlbug@perl.org|mailto:perlbug@perl.org>.

=head3 L<perlguts>

=over 4

=item *

Details of the various stacks within the perl interpreter are now explained
here.

=back

Additionally, the following selected changes have been made:

=head3 URLs have been changed to https:// and stale links have been updated

=over 4

=item *

Where applicable, the URLs in the documentation have been moved from using the
http:// protocol to https:// .  This also affects the location of the bug
tracker at L<https://rt.perl.org>.

=item *

Some links to OS/2 libraries, Address Sanitizer and other system tools had gone
stale.  These have been updated with working links.

=item *

Some links to old mails on perl5-porters had gone stale.  These have been
updated with working links.

=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 Changes to Existing Diagnostics

=over 4

=item *

L<Can't use global %s in %s|perldiag/"Can't use global %s in %s">

This error message has been slightly reformatted from the original C<Can't use
global %s in "%s">, and in particular misleading error messages like C<Can't
use global $_ in "my"> are now rendered as C<Can't use global $_ in subroutine
signature>.

=item *

L<Constants from lexical variables potentially modified elsewhere are no longer permitted|perldiag/"Constants from lexical variables potentially modified elsewhere are no longer permitted">

This error message replaces the former C<Constants from lexical variables
potentially modified elsewhere are deprecated.  This will not be allowed in Perl
5.32> to reflect the fact that this previously deprecated usage has now been
transformed into an exception.  The message's classification has also been
updated from D (deprecated) to F (fatal).

See also L</Incompatible Changes>.

=back

=head1 Configuration and Compilation

=over 4

=item *

Perl now no longer probes for C<d_u32align>, defaulting to C<define> on all
platforms.  This check was error prone when it was done, which was on 32-bit
platforms only.
L<[perl #133495]|https://rt.perl.org/Ticket/Display.html?id=133495>.

=item *

Documentation and hints for building perl on Z/OS (native EBCDIC) have been
updated.  Still work in progress.

=item *

A new probe for C<malloc_usable_size> has been added.

=back

=head1 Testing

Tests were added and changed to reflect the other additions and changes in this
release.

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item Windows

=over 4

=item *

Support for building perl with Visual C++ 6.0 has now been removed.

=item *

Building perl with Visual C++ 2013 and earlier was broken in the previous
release but has now been fixed.

=back

=back

=head1 Internal Changes

=over 4

=item *

Added the C<<PL_curstackinfo->si_cxsubix>> field.  This records the stack index
of the most recently pushed sub/format/eval context.  It is set and restored
automatically by C<cx_pushsub()>, C<cx_popsub()> etc., but would need to be
manually managed if you do any unusual manipulation of the context stack.

=item *

Various macros dealing with character type classification and changing case
where the input is encoded in UTF-8 now require an extra parameter to prevent
potential reads beyond the end of the buffer.  Use of these has generated a
deprecation warning since Perl 5.26.  Details are in
L<perldeprecation/In XS code, use of various macros dealing with UTF-8.>

=back

=head1 Acknowledgements

Perl 5.31.5 represents approximately 4 weeks of development since Perl 5.31.4
and contains approximately 27,000 lines of changes across 610 files from 15
authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 9,500 lines of changes to 150 .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 5.31.5:

Dagfinn Ilmari Mannsåker, David Mitchell, H.Merijn Brand, James E Keenan, Karl
Williamson, Matt Turner, Max Maischein, Nicolas R., Pali, Paul Evans, Paul
Marquess, Peter Eisentraut, Steve Hay, Tomasz Konojacki, 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://rt.perl.org/>.  There may also be information at
L<https://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
