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 feature is
29 L<[perl #13173]|https://github.com/Perl/perl5/issues/13173>.
31 =item Pluggable keywords
33 The ticket for this feature is
34 L<[perl #13199]|https://github.com/Perl/perl5/issues/13199>.
36 See L<perlapi/PL_keyword_plugin> for the mechanism.
38 Introduced in Perl 5.11.2
40 =item Regular Expression Set Operations
42 Introduced in Perl 5.18
44 The ticket for this feature is
45 L<[perl #13197]|https://github.com/Perl/perl5/issues/13197>.
47 See also: L<perlrecharclass/Extended Bracketed Character Classes>
49 Using this feature triggers warnings in the category
50 C<experimental::regex_sets>.
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 feature 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 feature 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 feature 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 See L<re/'strict' mode>
95 =item The <:win32> IO pseudolayer
97 The ticket for this feature is
98 L<[perl #13198]|https://github.com/Perl/perl5/issues/13198>.
100 See also L<perlrun/PERLIO>
102 =item Declaring a reference to a variable
104 Introduced in Perl 5.26.0
106 Using this feature triggers warnings in the category
107 C<experimental::declared_refs>.
109 The ticket for this feature is
110 L<[perl #15458]|https://github.com/Perl/perl5/issues/15458>.
112 See also: L<perlref/Declaring a Reference to a Variable>
114 =item There is an C<installhtml> target in the Makefile.
116 The ticket for this feature is
117 L<[perl #12726]|https://github.com/Perl/perl5/issues/12726>.
119 =item (Limited) Variable-length look-behind
121 Introduced in Perl 5.30.0. Variability of up to 255 characters is
124 Using this feature triggers warnings in the category
125 C<experimental::vlb>.
127 See also: L<perlre/(*positive_lookbehind:I<pattern>)> and
128 L<perlre/(*negative_lookbehind:I<pattern>)>
130 =item isa infix operator
132 Introduced in Perl 5.32.0.
134 Using this feature triggers warnings in the category
135 C<experimental::isa>.
137 The ticket for this feature is
138 L<[perl #17200]|https://github.com/Perl/perl5/issues/17200>
142 =head2 Accepted features
144 These features were so wildly successful and played so well with others that
145 we decided to remove their experimental status and admit them as full, stable
146 features in the world of Perl, lavishing all the benefits and luxuries thereof.
147 They are also awarded +5 Stability and +3 Charisma.
153 Introduced in Perl 5.005
155 =item die accepts a reference
157 Introduced in Perl 5.005
161 Introduced in Perl 5.6.0
163 See also L<perldebug>, L<perldebtut>
165 =item Weak references
167 Introduced in Perl 5.6.0
169 =item Internal file glob
171 Introduced in Perl 5.6.0
173 =item fork() emulation
175 Introduced in Perl 5.6.1
179 =item -Dusemultiplicity -Duseithreads
181 Introduced in Perl 5.6.0
183 Accepted in Perl 5.8.0
185 =item Support for long doubles
187 Introduced in Perl 5.6.0
189 Accepted in Perl 5.8.1
191 =item The C<\N> regex character class
193 The C<\N> character class, not to be confused with the named character
194 sequence C<\N{NAME}>, denotes any non-newline character in a regular
197 Introduced in Perl 5.12
199 Exact version of acceptance unclear, but no later than Perl 5.18.
201 =item C<(?{code})> and C<(??{ code })>
203 Introduced in Perl 5.6.0
205 Accepted in Perl 5.20.0
209 =item Linux abstract Unix domain sockets
211 Introduced in Perl 5.9.2
213 Accepted before Perl 5.20.0. The Socket library is now primarily maintained
214 on CPAN, rather than in the perl core.
218 =item Lvalue subroutines
220 Introduced in Perl 5.6.0
222 Accepted in Perl 5.20.0
226 =item Backtracking control verbs
230 Introduced in Perl 5.10
232 Accepted in Perl 5.20.0
234 =item The <:pop> IO pseudolayer
236 See also L<perlrun/PERLIO>
238 Accepted in Perl 5.20.0
240 =item C<\s> in regexp matches vertical tab
242 Accepted in Perl 5.22.0
244 =item Postfix dereference syntax
246 Introduced in Perl 5.20.0
248 Accepted in Perl 5.24.0
250 =item Lexical subroutines
252 Introduced in Perl 5.18.0
254 Accepted in Perl 5.26.0
256 =item String- and number-specific bitwise operators
258 Introduced in Perl 5.22.0
260 Accepted in Perl 5.28.0
262 =item Alphabetic assertions
264 Introduced in Perl 5.28.0
266 Accepted in Perl 5.32.0
270 Introduced in Perl 5.28.0
272 Accepted in Perl 5.32.0
276 =head2 Removed features
278 These features are no longer considered experimental and their functionality
279 has disappeared. It's your own fault if you wrote production programs using
280 these features after we explicitly told you not to (see L<perlpolicy>).
284 =item 5.005-style threading
286 Introduced in Perl 5.005
292 Introduced in Perl 5.005
294 Moved from Perl 5.9.0 to CPAN
296 =item The pseudo-hash data type
298 Introduced in Perl 5.6.0
300 Removed in Perl 5.9.0
302 =item GetOpt::Long Options can now take multiple values at once (experimental)
304 C<Getopt::Long> upgraded to version 2.35
306 Removed in Perl 5.8.8
310 The C<-A> command line switch
312 Introduced in Perl 5.9.0
314 Removed in Perl 5.9.5
316 =item Test::Harness::Straps
318 Moved from Perl 5.10.1 to CPAN
322 The experimental C<legacy> pragma was swallowed by the C<feature> pragma.
324 Introduced in Perl 5.11.2
326 Removed in Perl 5.11.3
330 Using this feature triggered warnings in the category
331 C<experimental::lexical_topic>.
333 Introduced in Perl 5.10.0
335 Removed in Perl 5.24.0
337 =item Array and hash container functions accept references
339 Using this feature triggered warnings in the category
340 C<experimental::autoderef>.
342 Superseded by L</Postfix dereference syntax>.
344 Introduced in Perl 5.14.0
346 Removed in Perl 5.24.0
348 =item C<our> can have an experimental optional attribute C<unique>
350 Introduced in Perl 5.8.0
352 Deprecated in Perl 5.10.0
354 Removed in Perl 5.28.0
360 For a complete list of features check L<feature>.
364 brian d foy C<< <brian.d.foy@gmail.com> >>
366 SE<eacute>bastien Aperghis-Tramoni C<< <saper@cpan.org> >>
370 Copyright 2010, brian d foy C<< <brian.d.foy@gmail.com> >>
374 You can use and redistribute this document under the same terms as Perl