5 perlpolicy - Various and sundry policies and commitments related to the Perl core
9 This document is the master document which records all written
10 policies about how the Perl 5 Porters collectively develop and maintain
17 Subscribers to perl5-porters (the porters themselves) come in several flavours.
18 Some are quiet curious lurkers, who rarely pitch in and instead watch
19 the ongoing development to ensure they're forewarned of new changes or
20 features in Perl. Some are representatives of vendors, who are there
21 to make sure that Perl continues to compile and work on their
22 platforms. Some patch any reported bug that they know how to fix,
23 some are actively patching their pet area (threads, Win32, the regexp
24 -engine), while others seem to do nothing but complain. In other
25 words, it's your usual mix of technical people.
27 Over this group of porters presides Larry Wall. He has the final word
28 in what does and does not change in any of the Perl programming languages.
29 These days, Larry spends most of his time on Perl 6, while Perl 5 is
30 shepherded by a "pumpking", a porter responsible for deciding what
31 goes into each release and ensuring that releases happen on a regular
34 Larry sees Perl development along the lines of the US government:
35 there's the Legislature (the porters), the Executive branch (the
36 -pumpking), and the Supreme Court (Larry). The legislature can
37 discuss and submit patches to the executive branch all they like, but
38 the executive branch is free to veto them. Rarely, the Supreme Court
39 will side with the executive branch over the legislature, or the
40 legislature over the executive branch. Mostly, however, the
41 legislature and the executive branch are supposed to get along and
42 work out their differences without impeachment or court cases.
44 You might sometimes see reference to Rule 1 and Rule 2. Larry's power
45 as Supreme Court is expressed in The Rules:
51 Larry is always by definition right about how Perl should behave.
52 This means he has final veto power on the core functionality.
56 Larry is allowed to change his mind about any matter at a later date,
57 regardless of whether he previously invoked Rule 1.
61 Got that? Larry is always right, even when he was wrong. It's rare
62 to see either Rule exercised, but they are often alluded to.
64 =head1 MAINTENANCE AND SUPPORT
66 Perl 5 is developed by a community, not a corporate entity. Every change
67 contributed to the Perl core is the result of a donation. Typically, these
68 donations are contributions of code or time by individual members of our
69 community. On occasion, these donations come in the form of corporate
70 or organizational sponsorship of a particular individual or project.
72 As a volunteer organization, the commitments we make are heavily dependent
73 on the goodwill and hard work of individuals who have no obligation to
76 That being said, we value Perl's stability and security and have long
77 had an unwritten covenant with the broader Perl community to support
78 and maintain releases of Perl.
80 This document codifies the support and maintenance commitments that
81 the Perl community should expect from Perl's developers:
87 We "officially" support the two most recent stable release series. 5.14.x
88 and earlier are now out of support. As of the release of 5.20.0, we will
89 "officially" end support for Perl 5.16.x, other than providing security
90 updates as described below.
94 To the best of our ability, we will attempt to fix critical issues
95 in the two most recent stable 5.x release series. Fixes for the
96 current release series take precedence over fixes for the previous
101 To the best of our ability, we will provide "critical" security patches
102 / releases for any major version of Perl whose 5.x.0 release was within
103 the past three years. We can only commit to providing these for the
104 most recent .y release in any 5.x.y series.
108 We will not provide security updates or bug fixes for development
113 We encourage vendors to ship the most recent supported release of
114 Perl at the time of their code freeze.
118 As a vendor, you may have a requirement to backport security fixes
119 beyond our 3 year support commitment. We can provide limited support and
120 advice to you as you do so and, where possible will try to apply
121 those patches to the relevant -maint branches in git, though we may or
122 may not choose to make numbered releases or "official" patches
123 available. Contact us at E<lt>perl5-security-report@perl.orgE<gt>
124 to begin that process.
128 =head1 BACKWARD COMPATIBILITY AND DEPRECATION
130 Our community has a long-held belief that backward-compatibility is a
131 virtue, even when the functionality in question is a design flaw.
133 We would all love to unmake some mistakes we've made over the past
134 decades. Living with every design error we've ever made can lead
135 to painful stagnation. Unwinding our mistakes is very, very
136 difficult. Doing so without actively harming our users is
139 Lately, ignoring or actively opposing compatibility with earlier versions
140 of Perl has come into vogue. Sometimes, a change is proposed which
141 wants to usurp syntax which previously had another meaning. Sometimes,
142 a change wants to improve previously-crazy semantics.
144 Down this road lies madness.
146 Requiring end-user programmers to change just a few language constructs,
147 even language constructs which no well-educated developer would ever
148 intentionally use is tantamount to saying "you should not upgrade to
149 a new release of Perl unless you have 100% test coverage and can do a
150 full manual audit of your codebase." If we were to have tools capable of
151 reliably upgrading Perl source code from one version of Perl to another,
152 this concern could be significantly mitigated.
154 We want to ensure that Perl continues to grow and flourish in the coming
155 years and decades, but not at the expense of our user community.
157 Existing syntax and semantics should only be marked for destruction in
158 very limited circumstances. If they can be easily replaced, are
159 believed to be very rarely used, and stand in the way of actual
160 improvement to the Perl language or perl interpreter, they may be
161 considered for removal. When in doubt, caution dictates that we will
162 favor backward compatibility. When a feature is deprecated, a
163 statement of reasoning describing the decision process will be posted,
164 and a link to it will be provided in the relevant perldelta documents.
166 Using a lexical pragma to enable or disable legacy behavior should be
167 considered when appropriate, and in the absence of any pragma legacy
168 behavior should be enabled. Which backward-incompatible changes are
169 controlled implicitly by a 'use v5.x.y' is a decision which should be
170 made by the pumpking in consultation with the community.
172 Historically, we've held ourselves to a far higher standard than
173 backward-compatibility -- bugward-compatibility. Any accident of
174 implementation or unintentional side-effect of running some bit of code
175 has been considered to be a feature of the language to be defended with
176 the same zeal as any other feature or functionality. No matter how
177 frustrating these unintentional features may be to us as we continue
178 to improve Perl, these unintentional features often deserve our
179 protection. It is very important that existing software written in
180 Perl continue to work correctly. If end-user developers have adopted a
181 bug as a feature, we need to treat it as such.
183 New syntax and semantics which don't break existing language constructs
184 and syntax have a much lower bar. They merely need to prove themselves
185 to be useful, elegant, well designed, and well tested. In most cases,
186 these additions will be marked as I<experimental> for some time. See
187 below for more on that.
191 To make sure we're talking about the same thing when we discuss the removal
192 of features or functionality from the Perl core, we have specific definitions
193 for a few words and phrases.
199 If something in the Perl core is marked as B<experimental>, we may change
200 its behaviour, deprecate or remove it without notice. While we'll always
201 do our best to smooth the transition path for users of experimental
202 features, you should contact the perl5-porters mailinglist if you find
203 an experimental feature useful and want to help shape its future.
205 Experimental features must be experimental in two stable releases before being
206 marked non-experimental. Experimental features will only have their
207 experimental status revoked when they no longer have any design-changing bugs
208 open against them and when they have remained unchanged in behavior for the
209 entire length of a development cycle. In other words, a feature present in
210 v5.20.0 may be marked no longer experimental in v5.22.0 if and only if its
211 behavior is unchanged throughout all of v5.21.
215 If something in the Perl core is marked as B<deprecated>, we may remove it
216 from the core in the future, though we might not. Generally, backward
217 incompatible changes will have deprecation warnings for two release
218 cycles before being removed, but may be removed after just one cycle if
219 the risk seems quite low or the benefits quite high.
222 Perl 5.12, deprecated features and modules warn the user as they're used.
223 When a module is deprecated, it will also be made available on CPAN.
224 Installing it from CPAN will silence deprecation warnings for that module.
226 If you use a deprecated feature or module and believe that its removal from
227 the Perl core would be a mistake, please contact the perl5-porters
228 mailinglist and plead your case. We don't deprecate things without a good
229 reason, but sometimes there's a counterargument we haven't considered.
230 Historically, we did not distinguish between "deprecated" and "discouraged"
235 From time to time, we may mark language constructs and features which we
236 consider to have been mistakes as B<discouraged>. Discouraged features
237 aren't currently candidates for removal, but
238 we may later deprecate them if they're found to stand in the way of a
239 significant improvement to the Perl core.
243 Once a feature, construct or module has been marked as deprecated, we
244 may remove it from the Perl core. Unsurprisingly,
245 we say we've B<removed> these things. When a module is removed, it will
246 no longer ship with Perl, but will continue to be available on CPAN.
250 =head1 MAINTENANCE BRANCHES
256 New releases of maint should contain as few changes as possible.
257 If there is any question about whether a given patch might merit
258 inclusion in a maint release, then it almost certainly should not
263 Portability fixes, such as changes to Configure and the files in
264 hints/ are acceptable. Ports of Perl to a new platform, architecture
265 or OS release that involve changes to the implementation are NOT
270 Acceptable documentation updates are those that correct factual errors,
271 explain significant bugs or deficiencies in the current implementation,
272 or fix broken markup.
276 Patches that add new warnings or errors or deprecate features
281 Patches that fix crashing bugs, assertion failures and
282 memory corruption that do not otherwise change Perl's
283 functionality or negatively impact performance are acceptable.
287 Patches that fix CVEs or security issues are acceptable, but should
288 be run through the perl5-security-report@perl.org mailing list
289 rather than applied directly.
293 Patches that fix regressions in perl's behavior relative to previous
294 releases are acceptable.
298 Updates to dual-life modules should consist of minimal patches to
299 fix crashing or security issues (as above).
303 Minimal patches that fix platform-specific test failures or build or
304 installation issues are acceptable. When these changes are made
305 to dual-life modules for which CPAN is canonical, any changes
306 should be coordinated with the upstream author.
310 New versions of dual-life modules should NOT be imported into maint.
311 Those belong in the next stable series.
315 Patches that add or remove features are not acceptable.
319 Patches that break binary compatibility are not acceptable. (Please
325 =head2 Getting changes into a maint branch
327 Historically, only the pumpking cherry-picked changes from bleadperl
328 into maintperl. This has scaling problems. At the same time,
329 maintenance branches of stable versions of Perl need to be treated with
330 great care. To that end, as of Perl 5.12, we have a new process for
333 Any committer may cherry-pick any commit from blead to a maint branch if
334 they send mail to perl5-porters announcing their intent to cherry-pick
335 a specific commit along with a rationale for doing so and at least two
336 other committers respond to the list giving their assent. (This policy
337 applies to current and former pumpkings, as well as other committers.)
339 =head1 CONTRIBUTED MODULES
342 =head2 A Social Contract about Artistic Control
344 What follows is a statement about artistic control, defined as the ability
345 of authors of packages to guide the future of their code and maintain
346 control over their work. It is a recognition that authors should have
347 control over their work, and that it is a responsibility of the rest of
348 the Perl community to ensure that they retain this control. It is an
349 attempt to document the standards to which we, as Perl developers, intend
350 to hold ourselves. It is an attempt to write down rough guidelines about
351 the respect we owe each other as Perl developers.
353 This statement is not a legal contract. This statement is not a legal
354 document in any way, shape, or form. Perl is distributed under the GNU
355 Public License and under the Artistic License; those are the precise legal
356 terms. This statement isn't about the law or licenses. It's about
357 community, mutual respect, trust, and good-faith cooperation.
359 We recognize that the Perl core, defined as the software distributed with
360 the heart of Perl itself, is a joint project on the part of all of us.
361 From time to time, a script, module, or set of modules (hereafter referred
362 to simply as a "module") will prove so widely useful and/or so integral to
363 the correct functioning of Perl itself that it should be distributed with
364 the Perl core. This should never be done without the author's explicit
365 consent, and a clear recognition on all parts that this means the module
366 is being distributed under the same terms as Perl itself. A module author
367 should realize that inclusion of a module into the Perl core will
368 necessarily mean some loss of control over it, since changes may
369 occasionally have to be made on short notice or for consistency with the
372 Once a module has been included in the Perl core, however, everyone
373 involved in maintaining Perl should be aware that the module is still the
374 property of the original author unless the original author explicitly
375 gives up their ownership of it. In particular:
381 The version of the module in the Perl core should still be considered the
382 work of the original author. All patches, bug reports, and so
383 forth should be fed back to them. Their development directions
384 should be respected whenever possible.
388 Patches may be applied by the pumpkin holder without the explicit
389 cooperation of the module author if and only if they are very minor,
390 time-critical in some fashion (such as urgent security fixes), or if
391 the module author cannot be reached. Those patches must still be
392 given back to the author when possible, and if the author decides on
393 an alternate fix in their version, that fix should be strongly
394 preferred unless there is a serious problem with it. Any changes not
395 endorsed by the author should be marked as such, and the contributor
396 of the change acknowledged.
400 The version of the module distributed with Perl should, whenever
401 possible, be the latest version of the module as distributed by the
402 author (the latest non-beta version in the case of public Perl
403 releases), although the pumpkin holder may hold off on upgrading the
404 version of the module distributed with Perl to the latest version
405 until the latest version has had sufficient testing.
409 In other words, the author of a module should be considered to have final
410 say on modifications to their module whenever possible (bearing in mind
411 that it's expected that everyone involved will work together and arrive at
412 reasonable compromises when there are disagreements).
414 As a last resort, however:
417 If the author's vision of the future of their module is sufficiently
418 different from the vision of the pumpkin holder and perl5-porters as a
419 whole so as to cause serious problems for Perl, the pumpkin holder may
420 choose to formally fork the version of the module in the Perl core from the
421 one maintained by the author. This should not be done lightly and
422 should B<always> if at all possible be done only after direct input
423 from Larry. If this is done, it must then be made explicit in the
424 module as distributed with the Perl core that it is a forked version and
425 that while it is based on the original author's work, it is no longer
426 maintained by them. This must be noted in both the documentation and
427 in the comments in the source of the module.
429 Again, this should be a last resort only. Ideally, this should never
430 happen, and every possible effort at cooperation and compromise should be
431 made before doing this. If it does prove necessary to fork a module for
432 the overall health of Perl, proper credit must be given to the original
433 author in perpetuity and the decision should be constantly re-evaluated to
434 see if a remerging of the two branches is possible down the road.
436 In all dealings with contributed modules, everyone maintaining Perl should
437 keep in mind that the code belongs to the original author, that they may
438 not be on perl5-porters at any given time, and that a patch is not
439 official unless it has been integrated into the author's copy of the
440 module. To aid with this, and with points #1, #2, and #3 above, contact
441 information for the authors of all contributed modules should be kept with
442 the Perl distribution.
444 Finally, the Perl community as a whole recognizes that respect for
445 ownership of code, respect for artistic control, proper credit, and active
446 effort to prevent unintentional code skew or communication gaps is vital
447 to the health of the community and Perl itself. Members of a community
448 should not normally have to resort to rules and laws to deal with each
449 other, and this document, although it contains rules so as to be clear, is
450 about an attitude and general approach. The first step in any dispute
451 should be open communication, respect for opposing views, and an attempt
452 at a compromise. In nearly every circumstance nothing more will be
453 necessary, and certainly no more drastic measure should be used until
454 every avenue of communication and discussion has failed.
459 Perl's documentation is an important resource for our users. It's
460 incredibly important for Perl's documentation to be reasonably coherent
461 and to accurately reflect the current implementation.
463 Just as P5P collectively maintains the codebase, we collectively
464 maintain the documentation. Writing a particular bit of documentation
465 doesn't give an author control of the future of that documentation.
466 At the same time, just as source code changes should match the style
467 of their surrounding blocks, so should documentation changes.
469 Examples in documentation should be illustrative of the concept
470 they're explaining. Sometimes, the best way to show how a
471 language feature works is with a small program the reader can
472 run without modification. More often, examples will consist
473 of a snippet of code containing only the "important" bits.
474 The definition of "important" varies from snippet to snippet.
475 Sometimes it's important to declare C<use strict> and C<use warnings>,
476 initialize all variables and fully catch every error condition.
477 More often than not, though, those things obscure the lesson
478 the example was intended to teach.
480 As Perl is developed by a global team of volunteers, our
481 documentation often contains spellings which look funny
482 to I<somebody>. Choice of American/British/Other spellings
483 is left as an exercise for the author of each bit of
484 documentation. When patching documentation, try to emulate
485 the documentation around you, rather than changing the existing
488 In general, documentation should describe what Perl does "now" rather
489 than what it used to do. It's perfectly reasonable to include notes
490 in documentation about how behaviour has changed from previous releases,
491 but, with very few exceptions, documentation isn't "dual-life" --
492 it doesn't need to fully describe how all old versions used to work.
494 =head1 STANDARDS OF CONDUCT
496 The official forum for the development of perl is the perl5-porters mailing
497 list, mentioned above, and its bugtracker at rt.perl.org. All participants in
498 discussion there are expected to adhere to a standard of conduct.
512 Civility is simple: stick to the facts while avoiding demeaning remarks and
513 sarcasm. It is not enough to be factual. You must also be civil. Responding
514 in kind to incivility is not acceptable.
516 If the list moderators tell you that you are not being civil, carefully
517 consider how your words have appeared before responding in any way. You may
518 protest, but repeated protest in the face of a repeatedly reaffirmed decision
521 Unacceptable behavior will result in a public and clearly identified warning.
522 Repeated unacceptable behavior will result in removal from the mailing list and
523 revocation of rights to update rt.perl.org. The first removal is for one
524 month. Subsequent removals will double in length. After six months with no
525 warning, a user's ban length is reset. Removals, like warnings, are public.
527 The list of moderators will be public knowledge. At present, it is:
528 Aaron Crane, Andy Dougherty, Ricardo Signes, Steffen Müller.
532 "Social Contract about Contributed Modules" originally by Russ Allbery E<lt>rra@stanford.eduE<gt> and the perl5-porters.