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maint policy: Reword/expand the ambiguous "as few changes as possible" phrase
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1=encoding utf8
2
48cb5b3a 3=head1 NAME
3c78fafa 4
9a7064ee 5perlpolicy - Various and sundry policies and commitments related to the Perl core
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6
7=head1 DESCRIPTION
8
9This document is the master document which records all written
10policies about how the Perl 5 Porters collectively develop and maintain
11the Perl core.
12
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13=head1 GOVERNANCE
14
15=head2 Perl 5 Porters
16
17Subscribers to perl5-porters (the porters themselves) come in several flavours.
18Some are quiet curious lurkers, who rarely pitch in and instead watch
19the ongoing development to ensure they're forewarned of new changes or
20features in Perl. Some are representatives of vendors, who are there
21to make sure that Perl continues to compile and work on their
22platforms. Some patch any reported bug that they know how to fix,
23some are actively patching their pet area (threads, Win32, the regexp
24-engine), while others seem to do nothing but complain. In other
25words, it's your usual mix of technical people.
26
27Over this group of porters presides Larry Wall. He has the final word
28in what does and does not change in any of the Perl programming languages.
29These days, Larry spends most of his time on Perl 6, while Perl 5 is
30shepherded by a "pumpking", a porter responsible for deciding what
31goes into each release and ensuring that releases happen on a regular
32basis.
33
34Larry sees Perl development along the lines of the US government:
35there's the Legislature (the porters), the Executive branch (the
36-pumpking), and the Supreme Court (Larry). The legislature can
37discuss and submit patches to the executive branch all they like, but
38the executive branch is free to veto them. Rarely, the Supreme Court
39will side with the executive branch over the legislature, or the
40legislature over the executive branch. Mostly, however, the
41legislature and the executive branch are supposed to get along and
42work out their differences without impeachment or court cases.
43
44You might sometimes see reference to Rule 1 and Rule 2. Larry's power
45as Supreme Court is expressed in The Rules:
46
47=over 4
48
49=item 1
50
51Larry is always by definition right about how Perl should behave.
52This means he has final veto power on the core functionality.
53
54=item 2
55
56Larry is allowed to change his mind about any matter at a later date,
57regardless of whether he previously invoked Rule 1.
58
59=back
60
61Got that? Larry is always right, even when he was wrong. It's rare
62to see either Rule exercised, but they are often alluded to.
63
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64=head1 MAINTENANCE AND SUPPORT
65
66Perl 5 is developed by a community, not a corporate entity. Every change
67contributed to the Perl core is the result of a donation. Typically, these
68donations are contributions of code or time by individual members of our
69community. On occasion, these donations come in the form of corporate
70or organizational sponsorship of a particular individual or project.
71
72As a volunteer organization, the commitments we make are heavily dependent
73on the goodwill and hard work of individuals who have no obligation to
74contribute to Perl.
75
3b4ebcde 76That being said, we value Perl's stability and security and have long
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77had an unwritten covenant with the broader Perl community to support
78and maintain releases of Perl.
79
80This document codifies the support and maintenance commitments that
81the Perl community should expect from Perl's developers:
82
83=over
84
85=item *
86
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87We "officially" support the two most recent stable release series. 5.14.x
88and 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
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90updates as described below.
91
92=item *
93
94To the best of our ability, we will attempt to fix critical issues
e26b5c49 95in the two most recent stable 5.x release series. Fixes for the
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96current release series take precedence over fixes for the previous
97release series.
98
99=item *
100
101To the best of our ability, we will provide "critical" security patches
f50f542d 102/ releases for any major version of Perl whose 5.x.0 release was within
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103the past three years. We can only commit to providing these for the
104most recent .y release in any 5.x.y series.
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105
106=item *
107
108We will not provide security updates or bug fixes for development
109releases of Perl.
110
111=item *
112
113We encourage vendors to ship the most recent supported release of
114Perl at the time of their code freeze.
115
116=item *
117
118As a vendor, you may have a requirement to backport security fixes
119beyond our 3 year support commitment. We can provide limited support and
120advice to you as you do so and, where possible will try to apply
121those patches to the relevant -maint branches in git, though we may or
122may not choose to make numbered releases or "official" patches
123available. Contact us at E<lt>perl5-security-report@perl.orgE<gt>
124to begin that process.
125
126=back
127
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128=head1 BACKWARD COMPATIBILITY AND DEPRECATION
129
130Our community has a long-held belief that backward-compatibility is a
131virtue, even when the functionality in question is a design flaw.
132
133We would all love to unmake some mistakes we've made over the past
134decades. Living with every design error we've ever made can lead
135to painful stagnation. Unwinding our mistakes is very, very
136difficult. Doing so without actively harming our users is
137nearly impossible.
138
139Lately, ignoring or actively opposing compatibility with earlier versions
140of Perl has come into vogue. Sometimes, a change is proposed which
141wants to usurp syntax which previously had another meaning. Sometimes,
339a461d 142a change wants to improve previously-crazy semantics.
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143
144Down this road lies madness.
145
146Requiring end-user programmers to change just a few language constructs,
147even language constructs which no well-educated developer would ever
148intentionally use is tantamount to saying "you should not upgrade to
149a new release of Perl unless you have 100% test coverage and can do a
150full manual audit of your codebase." If we were to have tools capable of
151reliably upgrading Perl source code from one version of Perl to another,
152this concern could be significantly mitigated.
153
154We want to ensure that Perl continues to grow and flourish in the coming
155years and decades, but not at the expense of our user community.
156
157Existing syntax and semantics should only be marked for destruction in
1adbeba0 158very limited circumstances. If they are believed to be very rarely used,
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159stand in the way of actual improvement to the Perl language or perl
160interpreter, and if affected code can be easily updated to continue
161working, they may be considered for removal. When in doubt, caution
162dictates that we will favor backward compatibility. When a feature is
163deprecated, a statement of reasoning describing the decision process
164will be posted, and a link to it will be provided in the relevant
165perldelta documents.
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166
167Using a lexical pragma to enable or disable legacy behavior should be
168considered when appropriate, and in the absence of any pragma legacy
169behavior should be enabled. Which backward-incompatible changes are
170controlled implicitly by a 'use v5.x.y' is a decision which should be
171made by the pumpking in consultation with the community.
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172
173Historically, we've held ourselves to a far higher standard than
174backward-compatibility -- bugward-compatibility. Any accident of
175implementation or unintentional side-effect of running some bit of code
176has been considered to be a feature of the language to be defended with
177the same zeal as any other feature or functionality. No matter how
178frustrating these unintentional features may be to us as we continue
179to improve Perl, these unintentional features often deserve our
180protection. It is very important that existing software written in
181Perl continue to work correctly. If end-user developers have adopted a
182bug as a feature, we need to treat it as such.
183
184New syntax and semantics which don't break existing language constructs
185and syntax have a much lower bar. They merely need to prove themselves
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186to be useful, elegant, well designed, and well tested. In most cases,
187these additions will be marked as I<experimental> for some time. See
188below for more on that.
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189
190=head2 Terminology
191
192To make sure we're talking about the same thing when we discuss the removal
193of features or functionality from the Perl core, we have specific definitions
194for a few words and phrases.
195
196=over
197
198=item experimental
199
200If something in the Perl core is marked as B<experimental>, we may change
201its behaviour, deprecate or remove it without notice. While we'll always
202do our best to smooth the transition path for users of experimental
203features, you should contact the perl5-porters mailinglist if you find
204an experimental feature useful and want to help shape its future.
205
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206Experimental features must be experimental in two stable releases before being
207marked non-experimental. Experimental features will only have their
208experimental status revoked when they no longer have any design-changing bugs
209open against them and when they have remained unchanged in behavior for the
210entire length of a development cycle. In other words, a feature present in
211v5.20.0 may be marked no longer experimental in v5.22.0 if and only if its
212behavior is unchanged throughout all of v5.21.
213
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214=item deprecated
215
216If something in the Perl core is marked as B<deprecated>, we may remove it
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217from the core in the future, though we might not. Generally, backward
218incompatible changes will have deprecation warnings for two release
219cycles before being removed, but may be removed after just one cycle if
220the risk seems quite low or the benefits quite high.
221
222As of
70e4a83b 223Perl 5.12, deprecated features and modules warn the user as they're used.
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224When a module is deprecated, it will also be made available on CPAN.
225Installing it from CPAN will silence deprecation warnings for that module.
226
227If you use a deprecated feature or module and believe that its removal from
228the Perl core would be a mistake, please contact the perl5-porters
229mailinglist and plead your case. We don't deprecate things without a good
230reason, but sometimes there's a counterargument we haven't considered.
231Historically, we did not distinguish between "deprecated" and "discouraged"
232features.
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233
234=item discouraged
235
236From time to time, we may mark language constructs and features which we
237consider to have been mistakes as B<discouraged>. Discouraged features
5c5fd8eb 238aren't currently candidates for removal, but
70e4a83b 239we may later deprecate them if they're found to stand in the way of a
9a7064ee 240significant improvement to the Perl core.
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241
242=item removed
243
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244Once a feature, construct or module has been marked as deprecated, we
245may remove it from the Perl core. Unsurprisingly,
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246we say we've B<removed> these things. When a module is removed, it will
247no longer ship with Perl, but will continue to be available on CPAN.
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248
249=back
48cb5b3a 250
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251=head1 MAINTENANCE BRANCHES
252
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253New releases of maintenance branches should only contain changes that fall into
254one of the "acceptable" categories set out below, but must not contain any
255changes that fall into one of the "unacceptable" categories. (For example, a
256fix for a crashing bug must not be included if it breaks binary compatibility.)
257
258It is not necessary to include every change meeting these criteria, and in
259general the focus should be on addressing security issues, crashing bugs,
260regressions and serious installation issues. The temptation to include a
261plethora of minor changes that don't affect the installation or execution of
262perl (e.g. spelling corrections in documentation) should be resisted in order
263to reduce the overall risk of overlooking something. The intention is to
264create maintenance releases which are both worthwhile and which users can have
265full confidence in the stability of. (A secondary concern is to avoid burning
266out the maint-pumpking or overwhelming other committers voting on changes to be
267included (see L</"Getting changes into a maint branch"> below).)
fcf56c88 268
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269The following types of change may be considered acceptable, as long as they do
270not also fall into any of the "unacceptable" categories set out below:
271
272=over
273
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274=item *
275
79f83602 276Patches that fix CVEs or security issues. These changes should
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277be run through the perl5-security-report@perl.org mailing list
278rather than applied directly.
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279
280=item *
281
4c0ef208 282Patches that fix crashing bugs, assertion failures and
a6f83414 283memory corruption but which do not otherwise change perl's
79f83602 284functionality or negatively impact performance.
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285
286=item *
287
56b40e63 288Patches that fix regressions in perl's behavior relative to previous
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289releases, no matter how old the regression, since some people may
290upgrade from very old versions of perl to the latest version.
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291
292=item *
293
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294Patches that fix anything which prevents or seriously impacts the build
295or installation of perl.
296
297=item *
298
64b35da5 299Portability fixes, such as changes to Configure and the files in
79f83602 300the hints/ folder.
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301
302=item *
303
e2b7b23f 304Minimal patches that fix platform-specific test failures.
27d0393b 305
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306=item *
307
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308Documentation updates that correct factual errors, explain significant
309bugs or deficiencies in the current implementation, or fix broken markup.
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310
311=item *
312
313Updates to dual-life modules should consist of minimal patches to
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314fix crashing bugs or security issues (as above). Any changes made to
315dual-life modules for which CPAN is canonical should be coordinated with
316the upstream author.
64b35da5 317
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318=back
319
320The following types of change are NOT acceptable:
321
322=over
323
324=item *
325
79f83602 326Patches that break binary compatibility. (Please talk to a pumpking.)
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327
328=item *
329
79f83602 330Patches that add or remove features.
c792d632 331
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332=item *
333
79f83602 334Patches that add new warnings or errors or deprecate features.
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335
336=item *
337
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338Ports of Perl to a new platform, architecture or OS release that
339involve changes to the implementation.
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340
341=item *
342
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343New versions of dual-life modules should NOT be imported into maint.
344Those belong in the next stable series.
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345
346=back
347
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348If there is any question about whether a given patch might merit
349inclusion in a maint release, then it almost certainly should not
350be included.
351
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352=head2 Getting changes into a maint branch
353
354Historically, only the pumpking cherry-picked changes from bleadperl
e566981e 355into maintperl. This has scaling problems. At the same time,
fcf56c88 356maintenance branches of stable versions of Perl need to be treated with
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357great care. To that end, as of Perl 5.12, we have a new process for
358maint branches.
fcf56c88 359
e566981e 360Any committer may cherry-pick any commit from blead to a maint branch if
fcf56c88 361they send mail to perl5-porters announcing their intent to cherry-pick
17c80487 362a specific commit along with a rationale for doing so and at least two
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363other committers respond to the list giving their assent. (This policy
364applies to current and former pumpkings, as well as other committers.)
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365
366=head1 CONTRIBUTED MODULES
367
368
369=head2 A Social Contract about Artistic Control
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370
371What follows is a statement about artistic control, defined as the ability
372of authors of packages to guide the future of their code and maintain
373control over their work. It is a recognition that authors should have
374control over their work, and that it is a responsibility of the rest of
375the Perl community to ensure that they retain this control. It is an
376attempt to document the standards to which we, as Perl developers, intend
377to hold ourselves. It is an attempt to write down rough guidelines about
378the respect we owe each other as Perl developers.
379
380This statement is not a legal contract. This statement is not a legal
381document in any way, shape, or form. Perl is distributed under the GNU
382Public License and under the Artistic License; those are the precise legal
383terms. This statement isn't about the law or licenses. It's about
384community, mutual respect, trust, and good-faith cooperation.
385
386We recognize that the Perl core, defined as the software distributed with
387the heart of Perl itself, is a joint project on the part of all of us.
aaa2bbb1 388From time to time, a script, module, or set of modules (hereafter referred
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389to simply as a "module") will prove so widely useful and/or so integral to
390the correct functioning of Perl itself that it should be distributed with
9a7064ee 391the Perl core. This should never be done without the author's explicit
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392consent, and a clear recognition on all parts that this means the module
393is being distributed under the same terms as Perl itself. A module author
394should realize that inclusion of a module into the Perl core will
395necessarily mean some loss of control over it, since changes may
396occasionally have to be made on short notice or for consistency with the
397rest of Perl.
398
399Once a module has been included in the Perl core, however, everyone
400involved in maintaining Perl should be aware that the module is still the
401property of the original author unless the original author explicitly
402gives up their ownership of it. In particular:
403
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404=over
405
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406=item *
407
9a7064ee 408The version of the module in the Perl core should still be considered the
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409work of the original author. All patches, bug reports, and so
410forth should be fed back to them. Their development directions
411should be respected whenever possible.
6ee623d5 412
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413=item *
414
415Patches may be applied by the pumpkin holder without the explicit
416cooperation of the module author if and only if they are very minor,
417time-critical in some fashion (such as urgent security fixes), or if
418the module author cannot be reached. Those patches must still be
419given back to the author when possible, and if the author decides on
420an alternate fix in their version, that fix should be strongly
421preferred unless there is a serious problem with it. Any changes not
422endorsed by the author should be marked as such, and the contributor
423of the change acknowledged.
424
425=item *
426
427The version of the module distributed with Perl should, whenever
428possible, be the latest version of the module as distributed by the
429author (the latest non-beta version in the case of public Perl
430releases), although the pumpkin holder may hold off on upgrading the
431version of the module distributed with Perl to the latest version
432until the latest version has had sufficient testing.
433
434=back
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435
436In other words, the author of a module should be considered to have final
437say on modifications to their module whenever possible (bearing in mind
438that it's expected that everyone involved will work together and arrive at
439reasonable compromises when there are disagreements).
440
441As a last resort, however:
442
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443
444If the author's vision of the future of their module is sufficiently
445different from the vision of the pumpkin holder and perl5-porters as a
446whole so as to cause serious problems for Perl, the pumpkin holder may
9a7064ee 447choose to formally fork the version of the module in the Perl core from the
48cb5b3a 448one maintained by the author. This should not be done lightly and
c4f5d98d 449should B<always> if at all possible be done only after direct input
48cb5b3a 450from Larry. If this is done, it must then be made explicit in the
9a7064ee 451module as distributed with the Perl core that it is a forked version and
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452that while it is based on the original author's work, it is no longer
453maintained by them. This must be noted in both the documentation and
454in the comments in the source of the module.
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455
456Again, this should be a last resort only. Ideally, this should never
457happen, and every possible effort at cooperation and compromise should be
458made before doing this. If it does prove necessary to fork a module for
459the overall health of Perl, proper credit must be given to the original
460author in perpetuity and the decision should be constantly re-evaluated to
461see if a remerging of the two branches is possible down the road.
462
463In all dealings with contributed modules, everyone maintaining Perl should
464keep in mind that the code belongs to the original author, that they may
465not be on perl5-porters at any given time, and that a patch is not
466official unless it has been integrated into the author's copy of the
467module. To aid with this, and with points #1, #2, and #3 above, contact
468information for the authors of all contributed modules should be kept with
469the Perl distribution.
470
471Finally, the Perl community as a whole recognizes that respect for
472ownership of code, respect for artistic control, proper credit, and active
473effort to prevent unintentional code skew or communication gaps is vital
474to the health of the community and Perl itself. Members of a community
475should not normally have to resort to rules and laws to deal with each
476other, and this document, although it contains rules so as to be clear, is
477about an attitude and general approach. The first step in any dispute
478should be open communication, respect for opposing views, and an attempt
479at a compromise. In nearly every circumstance nothing more will be
480necessary, and certainly no more drastic measure should be used until
481every avenue of communication and discussion has failed.
3c78fafa 482
70e4a83b 483
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484=head1 DOCUMENTATION
485
486Perl's documentation is an important resource for our users. It's
487incredibly important for Perl's documentation to be reasonably coherent
488and to accurately reflect the current implementation.
489
490Just as P5P collectively maintains the codebase, we collectively
491maintain the documentation. Writing a particular bit of documentation
492doesn't give an author control of the future of that documentation.
493At the same time, just as source code changes should match the style
494of their surrounding blocks, so should documentation changes.
495
496Examples in documentation should be illustrative of the concept
497they're explaining. Sometimes, the best way to show how a
498language feature works is with a small program the reader can
499run without modification. More often, examples will consist
500of a snippet of code containing only the "important" bits.
501The definition of "important" varies from snippet to snippet.
1bb8a155 502Sometimes it's important to declare C<use strict> and C<use warnings>,
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503initialize all variables and fully catch every error condition.
504More often than not, though, those things obscure the lesson
505the example was intended to teach.
506
507As Perl is developed by a global team of volunteers, our
508documentation often contains spellings which look funny
509to I<somebody>. Choice of American/British/Other spellings
510is left as an exercise for the author of each bit of
511documentation. When patching documentation, try to emulate
512the documentation around you, rather than changing the existing
513prose.
514
515In general, documentation should describe what Perl does "now" rather
516than what it used to do. It's perfectly reasonable to include notes
517in documentation about how behaviour has changed from previous releases,
9e9fdd5d 518but, with very few exceptions, documentation isn't "dual-life" --
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519it doesn't need to fully describe how all old versions used to work.
520
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521=head1 STANDARDS OF CONDUCT
522
523The official forum for the development of perl is the perl5-porters mailing
524list, mentioned above, and its bugtracker at rt.perl.org. All participants in
525discussion there are expected to adhere to a standard of conduct.
526
527=over 4
528
529=item *
530
531Always be civil.
532
533=item *
534
535Heed the moderators.
536
537=back
538
539Civility is simple: stick to the facts while avoiding demeaning remarks and
540sarcasm. It is not enough to be factual. You must also be civil. Responding
541in kind to incivility is not acceptable.
542
543If the list moderators tell you that you are not being civil, carefully
544consider how your words have appeared before responding in any way. You may
545protest, but repeated protest in the face of a repeatedly reaffirmed decision
546is not acceptable.
547
548Unacceptable behavior will result in a public and clearly identified warning.
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549Repeated unacceptable behavior will result in removal from the mailing list and
550revocation of rights to update rt.perl.org. The first removal is for one
551month. Subsequent removals will double in length. After six months with no
552warning, a user's ban length is reset. Removals, like warnings, are public.
17c80487 553
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554The list of moderators will be public knowledge. At present, it is:
555Aaron Crane, Andy Dougherty, Ricardo Signes, Steffen Müller.
3b4ebcde 556
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557=head1 CREDITS
558
3b4ebcde 559"Social Contract about Contributed Modules" originally by Russ Allbery E<lt>rra@stanford.eduE<gt> and the perl5-porters.
3c78fafa 560