=encoding utf8

=head1 NAME

perldelta - what is new for perl v5.35.11

=head1 DESCRIPTION

This document describes differences between the 5.35.10 release and the 5.35.11
release.

If you are upgrading from an earlier release such as 5.35.9, first read
L<perl53510delta>, which describes differences between 5.35.9 and 5.35.10.

=head1 Core Enhancements

=head2 New functions C<builtin::created_as_string> and C<builtin::created_as_number>

These new functions allow code to inspect whether a defined but non-referential
scalar value originated from an expression that was string-like in nature, or
number-like.  While most uses within Perl should not care about such
distinctions, this can be useful when serialising or encoding Perl data
structures for export to other languages or data formats where such a
distinction does matter.

=head2 Support for not sharing all keys in large hash tables.

This release includes support to build Perl so that it does not share all keys
in hash tables as has been historically the case since Perl v5.6.  The shared
key behavior was added to Perl originally to support having many objects with
the same keys without having to store each key many times.  For objects that
might be created hundreds or thousands of times this key sharing behavior can
result in using significantly less memory.  However, key sharing comes at the
cost of having to maintain an internal "master hash table" (PL_str_tab), and
having to do two store operations per key stored in a hash table.  It also can
result in surprising consequences with programs that fork, causing the master
hash table to be COWed (copy on write) into the memory space for each forked
process which can, in worst case, greatly increase the memory utilization of
such scripts.

The new behavior is an attempt to have our cake and eat it too.  Small hash
tables will continue to share keys, but once the hash table is used to store
more than a certain number of keys (currently 64) it will not share the new
keys that are added.  This should benefit scripts that build large hash tables,
especially those that do so in forked sub-processes.  The unshared mode is
triggered when the hash table is resized which is non-deterministic and depends
on the underlying hash function that perl has been built with and the seed used
by the current process so the exact circumstances when this new mode will be
enabled for a given hash will vary between different invocations of a script.

We are uncertain of the exact effects of this new mode and are keen to get
field reports about the consequences of enabling it.  We know that in many
cases not sharing keys speeds up scripts in general, and may result in a
reduction in memory consumption.  Code that builds large hashes where the keys
are stored in only one hash, for instance where the keys are message digests,
will likely benefit from this change by being faster and using less memory.
However, there are also circumstances where not sharing keys can significantly
increase memory consumption, such as where large numbers of keys are stored in
multiple hash tables at once.  We have data to suggest that not sharing keys
will reduce COW churn and overall memory consumption in scripts that fork and
construct large hash tables, however such scripts may also encounter a modest
speed penalty.  Overall, the consequences of not sharing keys will vary
depending on workload.  However, we believe that broadly speaking enabling this
feature will be beneficial for most of our users.  We would like to get data
from the field to validate our assumptions.

We are not enabling the new mode by default in this release as we want to
gather more data and obtain feedback from the field about how it affects
people's scripts, but our intention is to ship the next release of Perl,
version 5.38, with some form of this functionality enabled.  We are hopeful
that people will try to build their perls with this feature and provide us
feedback on the results.  This will help guide our next steps.  So please try
it and send feedback to the porters mailing list.

You can enable this new feature by passing

    -Accflags='-DPERL_USE_UNSHARED_KEYS_IN_LARGE_HASHES'

to F<Configure> during the Configuration process.

Big thanks to Nicholas Clark for all the hard work in implementing this new
feature.

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<B::Deparse> has been upgraded from version 1.63 to 1.64.

Deparse now tries harder to preserve the original type of numeric constants, so
!0 is deparsed as '!0' rather than '1', 2.0 is deparsed as '2.0' rather than
'2' etc.  The 'use/no warnings' lines for custom warnings categories are now
fully handled - in the previous few releases only a small number of categories
were correctly handled.

=item *

L<bignum> has been upgraded from version 0.64 to 0.65.

=item *

L<Compress::Raw::Bzip2> has been upgraded from version 2.101 to 2.103.

=item *

L<Compress::Raw::Zlib> has been upgraded from version 2.101 to 2.103.

=item *

L<Encode> has been upgraded from version 3.16 to 3.17.

=item *

L<IO> has been upgraded from version 1.49 to 1.49_01.

=item *

IO-Compress has been upgraded from version 2.102 to 2.106.

=item *

libnet has been upgraded from version 3.13 to 3.14.

=item *

L<Locale::Maketext> has been upgraded from version 1.30 to 1.31.

=item *

L<Math::BigInt> has been upgraded from version 1.999829 to 1.999830.

=item *

L<Math::BigRat> has been upgraded from version 0.2620 to 0.2621.

=item *

L<Module::CoreList> has been upgraded from version 5.20220320 to 5.20220420.

=item *

L<re> has been upgraded from version 0.42 to 0.43.

=item *

L<Socket> has been upgraded from version 2.032 to 2.033.

=item *

L<Storable> has been upgraded from version 3.25 to 3.26.

=item *

L<Test::Harness> has been upgraded from version 3.43 to 3.44.

=item *

L<Text::ParseWords> has been upgraded from version 3.30 to 3.31.

=item *

L<Time::HiRes> has been upgraded from version 1.9769 to 1.9770.

=item *

L<Unicode::Normalize> has been upgraded from version 1.30 to 1.31.

=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, open an issue
at L<https://github.com/Perl/perl5/issues>.

Additionally, the following selected changes have been made:

=head3 L<perlfunc>

=over 4

=item *

Add the new flow-control keywords (try, catch, finally and defer).

=back

=head2 Removed Documentation

=over

=item *

The long-obsolete F<README.macos> (aka the perlmacos manpage) has been removed.

=back

=head1 Configuration and Compilation

=over 4

=item *

A new question has been added to Configure, to ask if you want to build perl
with taint support.  If you say "no", then all taint features, such as the
B<-T> and B<-t> switches, will silently do nothing.  It defaults to "yes", so
if you run Configure accepting all defaults, you'll get a perl which supports
taint just like before.

If you're used to running Configure in "batch mode", here's how you'd build
Perl without taint support:

 ./Configure -des -Utaint_support

You can check the C<taint_support> key in the C<%Config> hash (in the B<Config>
module) to determine whether your perl supports taint.  If the key doesn't
exist in the hash, then you're almost certainly running under an older perl
which predates this change, and you can assume that taint is support.  See
L<perlsec> for more details.

=back

=head1 Testing

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

=head1 Selected Bug Fixes

=over 4

=item *

Early bailout from the inner one of a pair of nested lookbehinds could cause
the outer lookbehind to give the wrong answer.
[L<GH #19557|https://github.com/Perl/perl5/issues/19557>].

=item *

ACCEPT inside of a C<< (...)+ >> now works as expected.
[L<GH #19484|https://github.com/Perl/perl5/issues/19484>].

=back

=head1 Acknowledgements

Perl 5.35.11 represents approximately 4 weeks of development since Perl 5.35.10
and contains approximately 42,000 lines of changes across 360 files from 24
authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 36,000 lines of changes to 250 .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 5.35.11:

Bram, brian d foy, Dagfinn Ilmari Mannsåker, David Mitchell, Eugen Konkov,
Graham Knop, Hugo van der Sanden, James E Keenan, Karl Williamson, Leon
Timmermans, Magnus Woldrich, Neil Bowers, Niyas Sait, Paul Evans, Paul
Marquess, Ricardo Signes, Richard Leach, Sawyer X, Sergey Poznyakoff, Sisyphus,
Steve Hay, Todd Rinaldo, 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 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
