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=head1 NAME
perlexperiment - A listing of experimental features in Perl
=head1 DESCRIPTION
This document lists the current and past experimental features in the perl
core. Although all of these are documented with their appropriate topics,
this succinct listing gives you an overview and basic facts about their
status.
So far we've merely tried to find and list the experimental features and infer
their inception, versions, etc. There's a lot of speculation here.
=head2 Current experiments
=over 8
=item C<our> can now have an experimental optional attribute C<unique>
Introduced in Perl 5.8.0
Deprecated in Perl 5.10.0
The ticket for this feature is
L<[perl #119313]|https://rt.perl.org/rt3/Ticket/Display.html?id=119313>.
=item Smart match (C<~~>)
Introduced in Perl 5.10.0
Modified in Perl 5.10.1, 5.12.0
Using this feature triggers warnings in the category
C<experimental::smartmatch>.
The ticket for this feature is
L<[perl #119317]|https://rt.perl.org/rt3/Ticket/Display.html?id=119317>.
=item Pluggable keywords
The ticket for this feature is
L<[perl #119455]|https://rt.perl.org/rt3/Ticket/Display.html?id=119455>.
See L<perlapi/PL_keyword_plugin> for the mechanism.
Introduced in Perl 5.11.2
=item Regular Expression Set Operations
Introduced in Perl 5.18
The ticket for this feature is
L<[perl #119451]|https://rt.perl.org/rt3/Ticket/Display.html?id=119451>.
See also: L<perlrecharclass/Extended Bracketed Character Classes>
Using this feature triggers warnings in the category
C<experimental::regex_sets>.
=item Subroutine signatures
Introduced in Perl 5.20.0
Using this feature triggers warnings in the category
C<experimental::signatures>.
The ticket for this feature is
L<[perl #121481]|https://rt.perl.org/Ticket/Display.html?id=121481>.
=item Aliasing via reference
Introduced in Perl 5.22.0
Using this feature triggers warnings in the category
C<experimental::refaliasing>.
The ticket for this feature is
L<[perl #122947]|https://rt.perl.org/rt3/Ticket/Display.html?id=122947>.
See also: L<perlref/Assigning to References>
=item The "const" attribute
Introduced in Perl 5.22.0
Using this feature triggers warnings in the category
C<experimental::const_attr>.
The ticket for this feature is
L<[perl #123630]|https://rt.perl.org/rt3/Ticket/Display.html?id=123630>.
See also: L<perlsub/Constant Functions>
=item use re 'strict';
Introduced in Perl 5.22.0
Using this feature triggers warnings in the category
C<experimental::re_strict>.
See L<re/'strict' mode>
=item String- and number-specific bitwise operators
Introduced in Perl 5.22.0
See also: L<perlop/Bitwise String Operators>
Using this feature triggers warnings in the category
C<experimental::bitwise>.
The ticket for this feature is
L<[perl #123707]|https://rt.perl.org/rt3/Ticket/Display.html?id=123707>.
=item The <:win32> IO pseudolayer
The ticket for this feature is
L<[perl #119453]|https://rt.perl.org/rt3/Ticket/Display.html?id=119453>.
See also L<perlrun>
=item Declaring a reference to a variable
Introduced in Perl 5.26.0
Using this feature triggers warnings in the category
C<experimental::declared_refs>.
The ticket for this feature is
L<[perl #128654]|https://rt.perl.org/rt3/Ticket/Display.html?id=128654>.
See also: L<perlref/Declaring a Reference to a Variable>
=item There is an C<installhtml> target in the Makefile.
The ticket for this feature is
L<[perl #116487]|https://rt.perl.org/rt3/Ticket/Display.html?id=116487>.
=item Unicode in Perl on EBCDIC
=back
=head2 Accepted features
These features were so wildly successful and played so well with others that
we decided to remove their experimental status and admit them as full, stable
features in the world of Perl, lavishing all the benefits and luxuries thereof.
They are also awarded +5 Stability and +3 Charisma.
=over 8
=item 64-bit support
Introduced in Perl 5.005
=item die accepts a reference
Introduced in Perl 5.005
=item DB module
Introduced in Perl 5.6.0
See also L<perldebug>, L<perldebtut>
=item Weak references
Introduced in Perl 5.6.0
=item Internal file glob
Introduced in Perl 5.6.0
=item fork() emulation
Introduced in Perl 5.6.1
See also L<perlfork>
=item -Dusemultiplicity -Duseithreads
Introduced in Perl 5.6.0
Accepted in Perl 5.8.0
=item Support for long doubles
Introduced in Perl 5.6.0
Accepted in Perl 5.8.1
=item The C<\N> regex character class
The C<\N> character class, not to be confused with the named character
sequence C<\N{NAME}>, denotes any non-newline character in a regular
expression.
Introduced in Perl 5.12
Exact version of acceptance unclear, but no later than Perl 5.18.
=item C<(?{code})> and C<(??{ code })>
Introduced in Perl 5.6.0
Accepted in Perl 5.20.0
See also L<perlre>
=item Linux abstract Unix domain sockets
Introduced in Perl 5.9.2
Accepted before Perl 5.20.0. The Socket library is now primarily maintained
on CPAN, rather than in the perl core.
See also L<Socket>
=item Lvalue subroutines
Introduced in Perl 5.6.0
Accepted in Perl 5.20.0
See also L<perlsub>
=item Backtracking control verbs
C<(*ACCEPT)>
Introduced in Perl 5.10
Accepted in Perl 5.20.0
=item The <:pop> IO pseudolayer
See also L<perlrun>
Accepted in Perl 5.20.0
=item C<\s> in regexp matches vertical tab
Accepted in Perl 5.22.0
=item Postfix dereference syntax
Introduced in Perl 5.20.0
Accepted in Perl 5.24.0
=item Lexical subroutines
Introduced in Perl 5.18.0
Accepted in Perl 5.26.0
=back
=head2 Removed features
These features are no longer considered experimental and their functionality
has disappeared. It's your own fault if you wrote production programs using
these features after we explicitly told you not to (see L<perlpolicy>).
=over 8
=item 5.005-style threading
Introduced in Perl 5.005
Removed in Perl 5.10
=item perlcc
Introduced in Perl 5.005
Moved from Perl 5.9.0 to CPAN
=item The pseudo-hash data type
Introduced in Perl 5.6.0
Removed in Perl 5.9.0
=item GetOpt::Long Options can now take multiple values at once (experimental)
C<Getopt::Long> upgraded to version 2.35
Removed in Perl 5.8.8
=item Assertions
The C<-A> command line switch
Introduced in Perl 5.9.0
Removed in Perl 5.9.5
=item Test::Harness::Straps
Moved from Perl 5.10.1 to CPAN
=item C<legacy>
The experimental C<legacy> pragma was swallowed by the C<feature> pragma.
Introduced in Perl 5.11.2
Removed in Perl 5.11.3
=item Lexical C<$_>
Using this feature triggered warnings in the category
C<experimental::lexical_topic>.
Introduced in Perl 5.10.0
Removed in Perl 5.24.0
=item Array and hash container functions accept references
Using this feature triggered warnings in the category
C<experimental::autoderef>.
Superseded by L</Postfix dereference syntax>.
Introduced in Perl 5.14.0
Removed in Perl 5.24.0
=back
=head1 SEE ALSO
For a complete list of features check L<feature>.
=head1 AUTHORS
brian d foy C<< <brian.d.foy@gmail.com> >>
SE<eacute>bastien Aperghis-Tramoni C<< <saper@cpan.org> >>
=head1 COPYRIGHT
Copyright 2010, brian d foy C<< <brian.d.foy@gmail.com> >>
=head1 LICENSE
You can use and redistribute this document under the same terms as Perl
itself.
=cut