=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

=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>.

=item Lexical C<$_>

Introduced in Perl 5.10.0

Using this feature triggers warnings in the category
C<experimental::lexical_topic>.

=item Pluggable keywords

See L<perlapi/PL_keyword_plugin> for the mechanism.

Introduced in: Perl 5.11.2

=item Array and hash container functions accept references

Introduced in Perl 5.14.0

=item Lexical subroutines

Introduced in: Perl 5.18

See also: L<perlsub/Lexical Subroutines>

Using this feature triggers warnings in the category
C<experimental::lexical_subs>.

=item Regular Expression Set Operations

Introduced in: Perl 5.18

See also: L<perlrecharclass/Extended Bracketed Character Classes>

Using this feature triggers warnings in the category
C<experimental::regex_sets>.

=item C<\s> in regexp matches vertical tab

Introduced in Perl 5.18

=item The <:win32> IO pseudolayer

See also L<perlrun>

=item lex_start API

Introduced in Perl 5.13.7

=item internal API for C<%^H>

Introduced in Perl 5.13.7

See also C<cophh_> in L<perlapi>.

=item alloccopstash

Introduced in Perl 5.18.0

=item av_create_and_push

=item av_create_and_unshift_one

=item av_create_and_unshift_one

=item cop_store_label

Introduced in Perl 5.16.0

=item PL_keyword_plugin

=item gv_fetchmethod_*_flags

Introduced in Perl 5.16.0

=item hv_iternext_flags

=item lex_bufutf8

=item lex_discard_to

=item lex_grow_linestr

=item lex_next_chunk

=item lex_peek_unichar

=item lex_read_space

=item lex_read_to

=item lex_read_unichar

=item lex_stuff_pv

=item lex_stuff_pvn

=item lex_stuff_pvs

=item lex_stuff_sv

=item lex_unstuff

=item op_scope

=item op_lvalue

=item parse_fullstmt

=item parse_stmtseq

=item PL_parser-E<gt>bufend

=item PL_parser-E<gt>bufptr

=item PL_parser-E<gt>linestart

=item PL_parser-E<gt>linestr

=item Perl_signbit

=item pad_findmy

=item sv_utf8_decode

=item sv_utf8_downgrade

=item bytes_from_utf8

=item bytes_to_utf8

=item utf8_to_bytes

=item There is an C<installhtml> target in the Makefile.

=item Unicode in Perl on EBCDIC

See also: L<perlre/"Special Backtracking Control Verbs">

=item Code expressions, conditional expressions, and independent expressions in regexes

=item gv_try_downgrade

See also L<perlintern>

=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

=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: 5.11.2

Removed in: 5.11.3

=back

=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