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[p5sagit/p5-mst-13.2.git] / pod / perl5112delta.pod

=head1 NAME

perldelta - what is new for perl v5.11.2

=head1 DESCRIPTION

This document describes differences between the 5.11.1 release and
the 5.11.2 release.

=head1 Core Enhancements

=head2 qr overloading

It is now possible to overload the C<qr//> operator, that is, conversion
to regexp, like it was already possible to overload conversion to
boolean, string or number of objects. It is invoked when an object
appears on the right hand side of the C<=~> operator, or when it is
interpolated into a regexp. See L<overload>.

=head2 Pluggable keywords

Extension modules can now cleanly hook into the Perl parser to define new
kinds of keyword-headed expression and compound statement. The syntax
following the keyword is defined entirely by the extension. This allow
a completely non-Perl sublanguage to be parsed inline, with the right
ops cleanly generated. This feature is currently considered experimental.

See L<perlapi/PL_keyword_plugin> for the mechanism. The Perl core source
distribution also includes a new module L<XS::APItest::KeywordRPN>, which
implements reverse Polish notation arithmetic via pluggable keywords.
This module is mainly used for test purposes, and is not normally
installed, but also serves as an example of how to use the new mechanism.

=head2 Lexer API

We have added a public API for the lowest layers of lexing. This is meant
to provide a solid foundation for the parsing that Devel::Declare and
similar modules do, and it complements the pluggable keyword mechanism.
The API consists of some existing variables combined with some new functions,
all marked as experimental (which making them public certainly is).

=head2 APIs for more internals

The lowest layers of the lexer and parts of the pad system now have C
APIs available to XS extensions. These are necessary to support proper
use of pluggable keywords, but have other uses too. The new APIs are
experimental, and only cover a small proportion of what would be necessary
to take full advantage of the core's facilities in these areas. It is
intended that the Perl 5.13 development cycle will see the addition of
a full range of clean, supported interfaces.

=head2 Overridable function lookup

Where an extension module hooks the creation of rv2cv ops to modify
the subroutine lookup process, this now works correctly for bareword
subroutine calls. This means that prototypes on subroutines referenced
this way will be processed correctly. (Previously bareword subroutine
names were initially looked up, for parsing purposes, by an unhookable
mechanism, so extensions could only properly influence subroutine names
that appeared with an C<&> sigil.)

=head1 Modules and Pragmata

=head2 New Modules and Pragmata

=over 4

=item C<legacy>

Preserves legacy behaviors or enable new non-default behaviors.
Currently the only behaviour concerns semantics for the 128 characters
on ASCII systems that have the 8th bit set.

=back

=head2 Pragmata Changes

=over 4

=item C<diagnostics>

Supports %.0f formatting internally.

=item C<overload>

Allow overloading of 'qr'.

=back

=head2 Updated Modules

=over 4

=item C<B::Concise>

=item C<B::Deparse>

=item C<Carp>

=item C<Compress::Zlib>

=item C<CPANPLUS>

=item C<DBM_Filter>

=item C<Encode>

=item C<ExtUtils::CBuilder>

=item C<Env>

=item C<Exporter>

=item C<File::Fetch>

=item C<I8N::Langinfo>

=item C<I8N::LangTags>

=item C<IO::Compress>

=item C<IPC::Cmd>

=item C<List::Util>

=item C<Locale::Maketext>

=item C<Module::Build>

Updated to 0.35_08.

=item C<Module::CoreList>

=item C<Pod::Perldoc>

=item C<Pod::Simple>

=item C<Scalar::Util>

=item C<Switch>

=item C<XS::APItest>

=back

=head1 Utility Changes

=over 4

=item F<a2p>

Fixed bugs with the match() operator in list context, remove mention
of $[.

=back

=head1 Performance Enhancements

=over 4

=item *

Reversing an array to itself (as in C<@a = reverse @a>) in void context now
happens in-place and is several orders of magnitude faster than it used to be.
It will also preserve non-existent elements whenever possible, i.e. for non
magical arrays or tied arrays with C<EXISTS> and C<DELETE> methods.

=back

=head1 New or Changed Diagnostics

Several new diagnostics, see L<perldiag> for details.

=over 4

=item C<Bad plugin affecting keyword '%s'>

=item C<gmtime(%.0f) too large>

=item C<Lexing code attempted to stuff non-Latin-1 character into Latin-1 input>

=item C<Lexing code internal error (%s)>

=item C<localtime(%.0f) too large>

=item C<Overloaded dereference did not return a reference>

=item C<Overloaded qr did not return a REGEXP>

=item C<Perl_pmflag() is deprecated, and will be removed from the XS API>

=back

One diagnostic has been removed:

=over 4

=item C<Runaway format>

=back

=head1 Changed Internals

=over 4

=item *

C<Perl_pmflag> has been removed from the public API. Calling it now generates
a deprecation warning, and it will be removed in a future release. Although
listed as part of the API, it was never documented, and only ever used in
F<toke.c>, and prior to 5.10, F<regcomp.c>. In core, it has been replaced by a
static function.

=back

=head1 New Tests

=over 4

=item F<t/op/while_readdir.t>

Test that a bare readdir in while loop sets $_.

=back

=head1 Known Problems

=over 4

=item Known test failures on VMS

Perl 5.11.2 fails a small set of core and CPAN tests as of this release.
With luck, that'll be sorted out for 5.11.3.

=back

=head1 Deprecations

The following items are now deprecated.

=head2 Use of C<:=> to mean an empty attribute list is now deprecated.

An accident of Perl's parser meant that these constructions were all equivalent:

    my $pi := 4;
    my $pi : = 4;
    my $pi :  = 4;

with the C<:> being treated as the start of an attribute list, which ends
before the C<=>. As whitespace is not significant here, all are parsed as an
empty attribute list, hence all the above are equivalent to, and better written
as

    my $pi = 4;

because no attribute processing is done for an empty list.

As is, this meant that C<:=> cannot be used as a new token, without silently
changing the meaning of existing code. Hence that particular form is now
deprecated, and will become a syntax error. If it is absolutely necessary to
have empty attribute lists (for example, because of a code generator) then
avoid the warning by adding a space before the C<=>.

=head1 Acknowledgements

Perl 5.11.2 represents approximately 3 weeks development since Perl 5.11.1
contains 29,992 lines of changes across 458 files from 38 authors and committers:

Abhijit Menon-Sen, Abigail, Ben Morrow, Bo Borgerson, Brad Gilbert, Bram,
Chris Williams, Craig A. Berry, Daniel Frederick Crisman, Dave Rolsky,
David E. Wheeler, David Golden, Eric Brine, Father Chrysostomos,
Frank Wiegand, Gerard Goossen, Gisle Aas, Graham Barr, Harmen, H.Merijn Brand,
Jan Dubois, Jerry D. Hedden, Jesse Vincent, Karl Williamson, Kevin Ryde,
Leon Brocard, Nicholas Clark, Paul Marquess, Philippe Bruhat,
Rafael Garcia-Suarez, Sisyphus, Steffen Mueller, Steve Hay, Steve Peters,
Vincent Pit, Yuval Kogman, Yves Orton, and Zefram.

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.

=head1 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://rt.perl.org/perlbug/ . There may also be
information at http://www.perl.org/ , the Perl Home Page.

If you believe you have an unreported bug, please run the B<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 please send
it to perl5-security-report@perl.org. This points to a closed subscription
unarchived mailing list, which includes all the core committers, who be able
to help assess the impact of issues, figure out a resolution, and help
co-ordinate the release of patches to mitigate or fix the problem across all
platforms on which Perl is supported. Please only use this address for
security issues in the Perl core, not for modules independently
distributed on CPAN.

=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.

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