[perl5.git] / pod / perlexperiment.pod

=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 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 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

=item Script runs

Introduced in Perl 5.28.0

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

See also: L<perlre/Script Runs>

=item Alpabetic assertions

Introduced in Perl 5.28.0

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

See also: L<perlre/Extended Patterns>.

=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

=item String- and number-specific bitwise operators

Introduced in Perl 5.22.0

Accepted in Perl 5.28.0

=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

=item C<our> can have an experimental optional attribute C<unique>

Introduced in Perl 5.8.0

Deprecated in Perl 5.10.0

Removed in Perl 5.28.0

=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
Commit	Line	Data
42e73e1c	1	=head1 NAME
	2
	3	perlexperiment - A listing of experimental features in Perl
	4
	5	=head1 DESCRIPTION
	6
	7	This document lists the current and past experimental features in the perl
d1558b3e	8	core. Although all of these are documented with their appropriate topics,
42e73e1c	9	this succinct listing gives you an overview and basic facts about their
	10	status.
	11
fe8d2675	12	So far we've merely tried to find and list the experimental features and infer
d1558b3e	13	their inception, versions, etc. There's a lot of speculation here.
42e73e1c	14
	15	=head2 Current experiments
	16
	17	=over 8
	18
7896dde7	19	=item Smart match (C<~~>)
51c34fa4 RS	20
	21	Introduced in Perl 5.10.0
	22
7896dde7	23	Modified in Perl 5.10.1, 5.12.0
51c34fa4 RS	24
	25	Using this feature triggers warnings in the category
	26	C<experimental::smartmatch>.
	27
c77be11b RS	28	The ticket for this feature is
	29	L<[perl #119317]\|https://rt.perl.org/rt3/Ticket/Display.html?id=119317>.
	30
51c34fa4 RS	31	=item Pluggable keywords
51c34fa4 RS	32
57b503da RS	33	The ticket for this feature is
	34	L<[perl #119455]\|https://rt.perl.org/rt3/Ticket/Display.html?id=119455>.
	35
51c34fa4 RS	36	See L<perlapi/PL_keyword_plugin> for the mechanism.
51c34fa4 RS	37
aec1aee9	38	Introduced in Perl 5.11.2
51c34fa4	39
51c34fa4 RS	40	=item Regular Expression Set Operations
51c34fa4 RS	41
aec1aee9	42	Introduced in Perl 5.18
51c34fa4	43
ca888027 RS	44	The ticket for this feature is
	45	L<[perl #119451]\|https://rt.perl.org/rt3/Ticket/Display.html?id=119451>.
	46
51c34fa4 RS	47	See also: L<perlrecharclass/Extended Bracketed Character Classes>
	48
	49	Using this feature triggers warnings in the category
	50	C<experimental::regex_sets>.
	51
afdb3b14 RS	52	=item Subroutine signatures
	53
	54	Introduced in Perl 5.20.0
	55
	56	Using this feature triggers warnings in the category
	57	C<experimental::signatures>.
	58
	59	The ticket for this feature is
	60	L<[perl #121481]\|https://rt.perl.org/Ticket/Display.html?id=121481>.
	61
baabe3fb	62	=item Aliasing via reference
82848c10 FC	63
	64	Introduced in Perl 5.22.0
	65
	66	Using this feature triggers warnings in the category
baabe3fb	67	C<experimental::refaliasing>.
82848c10 FC	68
	69	The ticket for this feature is
	70	L<[perl #122947]\|https://rt.perl.org/rt3/Ticket/Display.html?id=122947>.
	71
	72	See also: L<perlref/Assigning to References>
	73
99734069 FC	74	=item The "const" attribute
	75
	76	Introduced in Perl 5.22.0
	77
	78	Using this feature triggers warnings in the category
	79	C<experimental::const_attr>.
	80
	81	The ticket for this feature is
1e50fc51	82	L<[perl #123630]\|https://rt.perl.org/rt3/Ticket/Display.html?id=123630>.
99734069 FC	83
	84	See also: L<perlsub/Constant Functions>
	85
1eac213a KW	86	=item use re 'strict';
	87
	88	Introduced in Perl 5.22.0
	89
	90	Using this feature triggers warnings in the category
	91	C<experimental::re_strict>.
	92
	93	See L<re/'strict' mode>
	94
706c19b7	95	=item The <:win32> IO pseudolayer
42e73e1c	96
a532d4a5 RS	97	The ticket for this feature is
	98	L<[perl #119453]\|https://rt.perl.org/rt3/Ticket/Display.html?id=119453>.
	99
42e73e1c	100	See also L<perlrun>
42e73e1c	101
5c703779 FC	102	=item Declaring a reference to a variable
	103
	104	Introduced in Perl 5.26.0
	105
	106	Using this feature triggers warnings in the category
	107	C<experimental::declared_refs>.
	108
	109	The ticket for this feature is
	110	L<[perl #128654]\|https://rt.perl.org/rt3/Ticket/Display.html?id=128654>.
	111
	112	See also: L<perlref/Declaring a Reference to a Variable>
	113
42e73e1c	114	=item There is an C<installhtml> target in the Makefile.
afb63838 RS	115
	116	The ticket for this feature is
	117	L<[perl #116487]\|https://rt.perl.org/rt3/Ticket/Display.html?id=116487>.
42e73e1c	118
	119	=item Unicode in Perl on EBCDIC
	120
dfc19b6b KW	121	=item Script runs
	122
	123	Introduced in Perl 5.28.0
	124
	125	Using this feature triggers warnings in the category
	126	C<experimental::script_run>.
	127
	128	See also: L<perlre/Script Runs>
	129
e7206367 KW	130	=item Alpabetic assertions
	131
	132	Introduced in Perl 5.28.0
	133
	134	Using this feature triggers warnings in the category
	135	C<experimental::alpha_assertions>.
	136
	137	See also: L<perlre/Extended Patterns>.
dfc19b6b	138
42e73e1c	139	=back
	140
	141	=head2 Accepted features
	142
	143	These features were so wildly successful and played so well with others that
	144	we decided to remove their experimental status and admit them as full, stable
51c34fa4	145	features in the world of Perl, lavishing all the benefits and luxuries thereof.
42e73e1c	146	They are also awarded +5 Stability and +3 Charisma.
	147
	148	=over 8
	149
51c34fa4	150	=item 64-bit support
42e73e1c	151
51c34fa4	152	Introduced in Perl 5.005
fe8d2675	153
51c34fa4	154	=item die accepts a reference
fe8d2675	155
51c34fa4	156	Introduced in Perl 5.005
fe8d2675 AT	157
	158	=item DB module
	159
	160	Introduced in Perl 5.6.0
	161
	162	See also L<perldebug>, L<perldebtut>
	163
	164	=item Weak references
	165
	166	Introduced in Perl 5.6.0
	167
	168	=item Internal file glob
	169
	170	Introduced in Perl 5.6.0
	171
51c34fa4	172	=item fork() emulation
fe8d2675	173
51c34fa4	174	Introduced in Perl 5.6.1
fe8d2675	175
51c34fa4	176	See also L<perlfork>
fe8d2675	177
3a0e7915 RS	178	=item -Dusemultiplicity -Duseithreads
	179
	180	Introduced in Perl 5.6.0
	181
	182	Accepted in Perl 5.8.0
	183
36d2f798 RS	184	=item Support for long doubles
	185
	186	Introduced in Perl 5.6.0
	187
	188	Accepted in Perl 5.8.1
	189
51c34fa4 RS	190	=item The C<\N> regex character class
	191
	192	The C<\N> character class, not to be confused with the named character
	193	sequence C<\N{NAME}>, denotes any non-newline character in a regular
	194	expression.
	195
3cb3bd66 RS	196	Introduced in Perl 5.12
	197
	198	Exact version of acceptance unclear, but no later than Perl 5.18.
fe8d2675	199
83f32aba RS	200	=item C<(?{code})> and C<(??{ code })>
	201
	202	Introduced in Perl 5.6.0
	203
	204	Accepted in Perl 5.20.0
	205
	206	See also L<perlre>
	207
e48e70eb RS	208	=item Linux abstract Unix domain sockets
	209
	210	Introduced in Perl 5.9.2
	211
	212	Accepted before Perl 5.20.0. The Socket library is now primarily maintained
	213	on CPAN, rather than in the perl core.
	214
	215	See also L<Socket>
	216
af7c9f88 RS	217	=item Lvalue subroutines
	218
	219	Introduced in Perl 5.6.0
	220
	221	Accepted in Perl 5.20.0
	222
	223	See also L<perlsub>
	224
b387afbc RS	225	=item Backtracking control verbs
	226
	227	C<(*ACCEPT)>
	228
aec1aee9	229	Introduced in Perl 5.10
b387afbc RS	230
	231	Accepted in Perl 5.20.0
	232
8a7bc862 RS	233	=item The <:pop> IO pseudolayer
	234
	235	See also L<perlrun>
	236
	237	Accepted in Perl 5.20.0
	238
779cf272 KW	239	=item C<\s> in regexp matches vertical tab
	240
	241	Accepted in Perl 5.22.0
	242
2ad792cd AC	243	=item Postfix dereference syntax
	244
	245	Introduced in Perl 5.20.0
	246
	247	Accepted in Perl 5.24.0
	248
06c4bad0 FC	249	=item Lexical subroutines
	250
	251	Introduced in Perl 5.18.0
	252
	253	Accepted in Perl 5.26.0
	254
193789ac FC	255	=item String- and number-specific bitwise operators
	256
	257	Introduced in Perl 5.22.0
	258
	259	Accepted in Perl 5.28.0
	260
42e73e1c	261	=back
	262
	263	=head2 Removed features
	264
	265	These features are no longer considered experimental and their functionality
	266	has disappeared. It's your own fault if you wrote production programs using
	267	these features after we explicitly told you not to (see L<perlpolicy>).
	268
	269	=over 8
	270
51c34fa4	271	=item 5.005-style threading
42e73e1c	272
51c34fa4	273	Introduced in Perl 5.005
42e73e1c	274
51c34fa4	275	Removed in Perl 5.10
42e73e1c	276
51c34fa4	277	=item perlcc
fe8d2675	278
51c34fa4	279	Introduced in Perl 5.005
fe8d2675	280
51c34fa4	281	Moved from Perl 5.9.0 to CPAN
fe8d2675	282
51c34fa4	283	=item The pseudo-hash data type
fe8d2675	284
51c34fa4	285	Introduced in Perl 5.6.0
fe8d2675	286
51c34fa4	287	Removed in Perl 5.9.0
fe8d2675 AT	288
	289	=item GetOpt::Long Options can now take multiple values at once (experimental)
	290
	291	C<Getopt::Long> upgraded to version 2.35
	292
	293	Removed in Perl 5.8.8
	294
51c34fa4	295	=item Assertions
fe8d2675	296
51c34fa4	297	The C<-A> command line switch
fe8d2675	298
51c34fa4	299	Introduced in Perl 5.9.0
fe8d2675	300
51c34fa4	301	Removed in Perl 5.9.5
fe8d2675	302
51c34fa4	303	=item Test::Harness::Straps
fe8d2675	304
51c34fa4	305	Moved from Perl 5.10.1 to CPAN
fe8d2675	306
51c34fa4	307	=item C<legacy>
fe8d2675	308
51c34fa4	309	The experimental C<legacy> pragma was swallowed by the C<feature> pragma.
fe8d2675	310
aec1aee9	311	Introduced in Perl 5.11.2
51c34fa4	312
aec1aee9	313	Removed in Perl 5.11.3
fe8d2675	314
f8b823eb DIM	315	=item Lexical C<$_>
f8b823eb DIM	316
74a78c10 AC	317	Using this feature triggered warnings in the category
	318	C<experimental::lexical_topic>.
	319
f8b823eb DIM	320	Introduced in Perl 5.10.0
	321
	322	Removed in Perl 5.24.0
	323
	324	=item Array and hash container functions accept references
	325
74a78c10 AC	326	Using this feature triggered warnings in the category
	327	C<experimental::autoderef>.
	328
f8b823eb DIM	329	Superseded by L</Postfix dereference syntax>.
	330
	331	Introduced in Perl 5.14.0
	332
	333	Removed in Perl 5.24.0
	334
85cd139f DIM	335	=item C<our> can have an experimental optional attribute C<unique>
	336
	337	Introduced in Perl 5.8.0
	338
	339	Deprecated in Perl 5.10.0
	340
	341	Removed in Perl 5.28.0
	342
42e73e1c	343	=back
42e73e1c	344
2b0121e1 AS	345	=head1 SEE ALSO
	346
	347	For a complete list of features check L<feature>.
	348
42e73e1c	349	=head1 AUTHORS
	350
	351	brian d foy C<< <brian.d.foy@gmail.com> >>
	352
fe8d2675 AT	353	SE<eacute>bastien Aperghis-Tramoni C<< <saper@cpan.org> >>
fe8d2675 AT	354
42e73e1c	355	=head1 COPYRIGHT
	356
	357	Copyright 2010, brian d foy C<< <brian.d.foy@gmail.com> >>
	358
	359	=head1 LICENSE
	360
	361	You can use and redistribute this document under the same terms as Perl
	362	itself.
	363
	364	=cut