3 perlexperiment - A listing of experimental features in Perl
7 This document lists the current and past experimental features in the perl
8 core. Although all of these are documented with their appropriate topics,
9 this succinct listing gives you an overview and basic facts about their
12 So far we've merely tried to find and list the experimental features and infer
13 their inception, versions, etc. There's a lot of speculation here.
15 =head2 Current experiments
19 =item Smart match (C<~~>)
21 Introduced in Perl 5.10.0
23 Modified in Perl 5.10.1, 5.12.0
25 Using this feature triggers warnings in the category
26 C<experimental::smartmatch>.
28 The ticket for this experiment is
29 L<[perl #13173]|https://github.com/Perl/perl5/issues/13173>.
31 =item Pluggable keywords
33 Introduced in Perl 5.11.2
35 See L<perlapi/PL_keyword_plugin> for the mechanism.
37 The ticket for this experiment is
38 L<[perl #13199]|https://github.com/Perl/perl5/issues/13199>.
40 =item Regular Expression Set Operations
42 Introduced in Perl 5.18
44 Using this feature triggers warnings in the category
45 C<experimental::regex_sets>.
47 The ticket for this experiment is
48 L<[perl #13197]|https://github.com/Perl/perl5/issues/13197>.
50 See also: L<perlrecharclass/Extended Bracketed Character Classes>
52 =item Subroutine signatures
54 Introduced in Perl 5.20.0
56 Using this feature triggers warnings in the category
57 C<experimental::signatures>.
59 The ticket for this experiment is
60 L<[perl #13681]|https://github.com/Perl/perl5/issues/13681>.
62 =item Aliasing via reference
64 Introduced in Perl 5.22.0
66 Using this feature triggers warnings in the category
67 C<experimental::refaliasing>.
69 The ticket for this experiment is
70 L<[perl #14150]|https://github.com/Perl/perl5/issues/14150>.
72 See also: L<perlref/Assigning to References>
74 =item The "const" attribute
76 Introduced in Perl 5.22.0
78 Using this feature triggers warnings in the category
79 C<experimental::const_attr>.
81 The ticket for this experiment is
82 L<[perl #14428]|https://github.com/Perl/perl5/issues/14428>.
84 See also: L<perlsub/Constant Functions>
86 =item use re 'strict';
88 Introduced in Perl 5.22.0
90 Using this feature triggers warnings in the category
91 C<experimental::re_strict>.
93 The ticket for this experiment is
94 L<[perl #18755]|https://github.com/Perl/perl5/issues/18755>
96 See L<re/'strict' mode>
98 =item Declaring a reference to a variable
100 Introduced in Perl 5.26.0
102 Using this feature triggers warnings in the category
103 C<experimental::declared_refs>.
105 The ticket for this experiment is
106 L<[perl #15458]|https://github.com/Perl/perl5/issues/15458>.
108 See also: L<perlref/Declaring a Reference to a Variable>
110 =item There is an C<installhtml> target in the Makefile.
112 The ticket for this experiment is
113 L<[perl #12726]|https://github.com/Perl/perl5/issues/12726>.
115 =item (Limited) Variable-length look-behind
117 Introduced in Perl 5.30.0.
119 Variability of up to 255 characters is handled.
121 Using this feature triggers warnings in the category
122 C<experimental::vlb>.
124 The ticket for this experiment is
125 L<[perl #18756]|https://github.com/Perl/perl5/issues/18756>.
127 See also: L<perlre/(*positive_lookbehind:I<pattern>)> and
128 L<perlre/(*negative_lookbehind:I<pattern>)>
130 =item Unicode private use character hooks
132 Introduced in Perl 5.30.0.
134 This feature is part of an interface intended for internal and experimental
135 use by the perl5 developers. You are unlikely to encounter it in the wild.
137 Using this feature triggers warnings in the category
138 C<experimental::private_use>.
140 The ticket for this experiment is
141 L<[perl #18758]|https://github.com/Perl/perl5/issues/18758>.
143 =item Unicode property wildcards
145 Introduced in Perl 5.30.0.
147 This feature allows regular expression matching against Unicode character
148 properties to be expressed more concisely.
150 Using this feature triggers warnings in the category
151 C<experimental::uniprop_wildcards>.
153 The ticket for this experiment is
154 L<[perl #18759]|https://github.com/Perl/perl5/issues/18759>.
156 =item isa infix operator
158 Introduced in Perl 5.32.0.
160 Using this feature triggers warnings in the category
161 C<experimental::isa>.
163 The ticket for this experiment is
164 L<[perl #18754]|https://github.com/Perl/perl5/issues/18754>
166 =item try/catch control structure
168 Introduced in Perl 5.34.0.
170 Using this feature triggers warnings in the category C<experimental::try>.
172 The ticket for this experiment is
173 L<[perl #18760]|https://github.com/Perl/perl5/issues/18760>
177 =head2 Accepted features
179 These features were so wildly successful and played so well with others that
180 we decided to remove their experimental status and admit them as full, stable
181 features in the world of Perl, lavishing all the benefits and luxuries thereof.
182 They are also awarded +5 Stability and +3 Charisma.
188 Introduced in Perl 5.005
190 =item die accepts a reference
192 Introduced in Perl 5.005
196 Introduced in Perl 5.6.0
198 See also L<perldebug>, L<perldebtut>
200 =item Weak references
202 Introduced in Perl 5.6.0
204 =item Internal file glob
206 Introduced in Perl 5.6.0
208 =item fork() emulation
210 Introduced in Perl 5.6.1
214 =item -Dusemultiplicity -Duseithreads
216 Introduced in Perl 5.6.0
218 Accepted in Perl 5.8.0
220 =item Support for long doubles
222 Introduced in Perl 5.6.0
224 Accepted in Perl 5.8.1
226 =item The C<\N> regex character class
228 The C<\N> character class, not to be confused with the named character
229 sequence C<\N{NAME}>, denotes any non-newline character in a regular
232 Introduced in Perl 5.12
234 Exact version of acceptance unclear, but no later than Perl 5.18.
236 =item C<(?{code})> and C<(??{ code })>
238 Introduced in Perl 5.6.0
240 Accepted in Perl 5.20.0
244 =item Linux abstract Unix domain sockets
246 Introduced in Perl 5.9.2
248 Accepted before Perl 5.20.0. The Socket library is now primarily maintained
249 on CPAN, rather than in the perl core.
253 =item Lvalue subroutines
255 Introduced in Perl 5.6.0
257 Accepted in Perl 5.20.0
261 =item Backtracking control verbs
265 Introduced in Perl 5.10
267 Accepted in Perl 5.20.0
269 =item The C<:pop> IO pseudolayer
271 See also L<perlrun/PERLIO>
273 Accepted in Perl 5.20.0
275 =item C<\s> in regexp matches vertical tab
277 Accepted in Perl 5.22.0
279 =item Postfix dereference syntax
281 Introduced in Perl 5.20.0
283 Accepted in Perl 5.24.0
285 =item Lexical subroutines
287 Introduced in Perl 5.18.0
289 Accepted in Perl 5.26.0
291 =item String- and number-specific bitwise operators
293 Introduced in Perl 5.22.0
295 Accepted in Perl 5.28.0
297 =item Alphabetic assertions
299 Introduced in Perl 5.28.0
301 Accepted in Perl 5.32.0
305 Introduced in Perl 5.28.0
307 Accepted in Perl 5.32.0
311 =head2 Removed features
313 These features are no longer considered experimental and their functionality
314 has disappeared. It's your own fault if you wrote production programs using
315 these features after we explicitly told you not to (see L<perlpolicy>).
319 =item 5.005-style threading
321 Introduced in Perl 5.005
327 Introduced in Perl 5.005
329 Moved from Perl 5.9.0 to CPAN
331 =item The pseudo-hash data type
333 Introduced in Perl 5.6.0
335 Removed in Perl 5.9.0
337 =item GetOpt::Long Options can now take multiple values at once (experimental)
339 C<Getopt::Long> upgraded to version 2.35
341 Removed in Perl 5.8.8
345 The C<-A> command line switch
347 Introduced in Perl 5.9.0
349 Removed in Perl 5.9.5
351 =item Test::Harness::Straps
353 Moved from Perl 5.10.1 to CPAN
357 The experimental C<legacy> pragma was swallowed by the C<feature> pragma.
359 Introduced in Perl 5.11.2
361 Removed in Perl 5.11.3
365 Using this feature triggered warnings in the category
366 C<experimental::lexical_topic>.
368 Introduced in Perl 5.10.0
370 Removed in Perl 5.24.0
372 =item Array and hash container functions accept references
374 Using this feature triggered warnings in the category
375 C<experimental::autoderef>.
377 Superseded by L</Postfix dereference syntax>.
379 Introduced in Perl 5.14.0
381 Removed in Perl 5.24.0
383 =item C<our> can have an experimental optional attribute C<unique>
385 Introduced in Perl 5.8.0
387 Deprecated in Perl 5.10.0
389 Removed in Perl 5.28.0
391 =item The C<:win32> IO pseudolayer
393 Introduced in Perl 5.8.0 (or before)
395 Removed in Perl 5.36.0
401 For a complete list of features check L<feature>.
405 brian d foy C<< <brian.d.foy@gmail.com> >>
407 SE<eacute>bastien Aperghis-Tramoni C<< <saper@cpan.org> >>
411 Copyright 2010, brian d foy C<< <brian.d.foy@gmail.com> >>
415 You can use and redistribute this document under the same terms as Perl