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PERLPOLICY(1pm)        Perl Programmers Reference Guide        PERLPOLICY(1pm)


       perlpolicy - Various and sundry policies and commitments related to the
       Perl core


       This document is the master document which records all written policies
       about how the Perl 5 Porters collectively develop and maintain the Perl


   Perl 5 Porters
       Subscribers to perl5-porters (the porters themselves) come in several
       flavours.  Some are quiet curious lurkers, who rarely pitch in and
       instead watch the ongoing development to ensure they're forewarned of
       new changes or features in Perl.  Some are representatives of vendors,
       who are there to make sure that Perl continues to compile and work on
       their platforms.  Some patch any reported bug that they know how to
       fix, some are actively patching their pet area (threads, Win32, the
       regexp -engine), while others seem to do nothing but complain.  In
       other words, it's your usual mix of technical people.

       Among these people are the core Perl team.  These are trusted
       volunteers involved in the ongoing development of the Perl language and
       interpreter.  They are not required to be language developers or

       Over this group of porters presides Larry Wall.  He has the final word
       in what does and does not change in any of the Perl programming
       languages.  These days, Larry spends most of his time on Raku, while
       Perl 5 is shepherded by a steering council of porters responsible for
       deciding what goes into each release and ensuring that releases happen
       on a regular basis.

       Larry sees Perl development along the lines of the US government:
       there's the Legislature (the porters, represented by the core team),
       the Executive branch (the steering council), and the Supreme Court
       (Larry).  The legislature can discuss and submit patches to the
       executive branch all they like, but the executive branch is free to
       veto them.  Rarely, the Supreme Court will side with the executive
       branch over the legislature, or the legislature over the executive
       branch.  Mostly, however, the legislature and the executive branch are
       supposed to get along and work out their differences without
       impeachment or court cases.

       You might sometimes see reference to Rule 1 and Rule 2.  Larry's power
       as Supreme Court is expressed in The Rules:

       1.  Larry is always by definition right about how Perl should behave.
           This means he has final veto power on the core functionality.

       2.  Larry is allowed to change his mind about any matter at a later
           date, regardless of whether he previously invoked Rule 1.

       Got that?  Larry is always right, even when he was wrong.  It's rare to
       see either Rule exercised, but they are often alluded to.

       For the specifics on how the members of the core team and steering
       council are elected or rotated, consult perlgov, which spells it all
       out in detail.


       Perl 5 is developed by a community, not a corporate entity. Every
       change contributed to the Perl core is the result of a donation.
       Typically, these donations are contributions of code or time by
       individual members of our community. On occasion, these donations come
       in the form of corporate or organizational sponsorship of a particular
       individual or project.

       As a volunteer organization, the commitments we make are heavily
       dependent on the goodwill and hard work of individuals who have no
       obligation to contribute to Perl.

       That being said, we value Perl's stability and security and have long
       had an unwritten covenant with the broader Perl community to support
       and maintain releases of Perl.

       This document codifies the support and maintenance commitments that the
       Perl community should expect from Perl's developers:

       o   We "officially" support the two most recent stable release series.
           5.26.x and earlier are now out of support.  As of the release of
           5.32.0, we will "officially" end support for Perl 5.28.x, other
           than providing security updates as described below.

       o   To the best of our ability, we will attempt to fix critical issues
           in the two most recent stable 5.x release series.  Fixes for the
           current release series take precedence over fixes for the previous
           release series.

       o   To the best of our ability, we will provide "critical" security
           patches / releases for any major version of Perl whose 5.x.0
           release was within the past three years.  We can only commit to
           providing these for the most recent .y release in any 5.x.y series.

       o   We will not provide security updates or bug fixes for development
           releases of Perl.

       o   We encourage vendors to ship the most recent supported release of
           Perl at the time of their code freeze.

       o   As a vendor, you may have a requirement to backport security fixes
           beyond our 3 year support commitment.  We can provide limited
           support and advice to you as you do so and, where possible will try
           to apply those patches to the relevant -maint branches in git,
           though we may or may not choose to make numbered releases or
           "official" patches available. See "SECURITY VULNERABILITY CONTACT
           INFORMATION" in perlsec for details on how to begin that process.


       Our community has a long-held belief that backward-compatibility is a
       virtue, even when the functionality in question is a design flaw.

       We would all love to unmake some mistakes we've made over the past
       decades.  Living with every design error we've ever made can lead to
       painful stagnation.  Unwinding our mistakes is very, very difficult.
       Doing so without actively harming our users is nearly impossible.

       Lately, ignoring or actively opposing compatibility with earlier
       versions of Perl has come into vogue.  Sometimes, a change is proposed
       which wants to usurp syntax which previously had another meaning.
       Sometimes, a change wants to improve previously-crazy semantics.

       Down this road lies madness.

       Requiring end-user programmers to change just a few language
       constructs, even language constructs which no well-educated developer
       would ever intentionally use is tantamount to saying "you should not
       upgrade to a new release of Perl unless you have 100% test coverage and
       can do a full manual audit of your codebase."  If we were to have tools
       capable of reliably upgrading Perl source code from one version of Perl
       to another, this concern could be significantly mitigated.

       We want to ensure that Perl continues to grow and flourish in the
       coming years and decades, but not at the expense of our user community.

       Existing syntax and semantics should only be marked for destruction in
       very limited circumstances.  If they are believed to be very rarely
       used, stand in the way of actual improvement to the Perl language or
       perl interpreter, and if affected code can be easily updated to
       continue working, they may be considered for removal.  When in doubt,
       caution dictates that we will favor backward compatibility.  When a
       feature is deprecated, a statement of reasoning describing the decision
       process will be posted, and a link to it will be provided in the
       relevant perldelta documents.

       Using a lexical pragma to enable or disable legacy behavior should be
       considered when appropriate, and in the absence of any pragma legacy
       behavior should be enabled.  Which backward-incompatible changes are
       controlled implicitly by a 'use v5.x.y' is a decision which should be
       made by the steering council in consultation with the community.

       Historically, we've held ourselves to a far higher standard than
       backward-compatibility -- bugward-compatibility.  Any accident of
       implementation or unintentional side-effect of running some bit of code
       has been considered to be a feature of the language to be defended with
       the same zeal as any other feature or functionality.  No matter how
       frustrating these unintentional features may be to us as we continue to
       improve Perl, these unintentional features often deserve our
       protection.  It is very important that existing software written in
       Perl continue to work correctly.  If end-user developers have adopted a
       bug as a feature, we need to treat it as such.

       New syntax and semantics which don't break existing language constructs
       and syntax have a much lower bar.  They merely need to prove themselves
       to be useful, elegant, well designed, and well tested.  In most cases,
       these additions will be marked as experimental for some time.  See
       below for more on that.

       To make sure we're talking about the same thing when we discuss the
       removal of features or functionality from the Perl core, we have
       specific definitions for a few words and phrases.

           If something in the Perl core is marked as experimental, we may
           change its behaviour, deprecate or remove it without notice. While
           we'll always do our best to smooth the transition path for users of
           experimental features, you should contact the perl5-porters
           mailinglist if you find an experimental feature useful and want to
           help shape its future.

           Experimental features must be experimental in two stable releases
           before being marked non-experimental.  Experimental features will
           only have their experimental status revoked when they no longer
           have any design-changing bugs open against them and when they have
           remained unchanged in behavior for the entire length of a
           development cycle.  In other words, a feature present in v5.20.0
           may be marked no longer experimental in v5.22.0 if and only if its
           behavior is unchanged throughout all of v5.21.

           If something in the Perl core is marked as deprecated, we may
           remove it from the core in the future, though we might not.
           Generally, backward incompatible changes will have deprecation
           warnings for two release cycles before being removed, but may be
           removed after just one cycle if the risk seems quite low or the
           benefits quite high.

           As of Perl 5.12, deprecated features and modules warn the user as
           they're used.  When a module is deprecated, it will also be made
           available on CPAN.  Installing it from CPAN will silence
           deprecation warnings for that module.

           If you use a deprecated feature or module and believe that its
           removal from the Perl core would be a mistake, please contact the
           perl5-porters mailinglist and plead your case.  We don't deprecate
           things without a good reason, but sometimes there's a
           counterargument we haven't considered.  Historically, we did not
           distinguish between "deprecated" and "discouraged" features.

           From time to time, we may mark language constructs and features
           which we consider to have been mistakes as discouraged.
           Discouraged features aren't currently candidates for removal, but
           we may later deprecate them if they're found to stand in the way of
           a significant improvement to the Perl core.

           Once a feature, construct or module has been marked as deprecated,
           we may remove it from the Perl core.  Unsurprisingly, we say we've
           removed these things.  When a module is removed, it will no longer
           ship with Perl, but will continue to be available on CPAN.


       New releases of maintenance branches should only contain changes that
       fall into one of the "acceptable" categories set out below, but must
       not contain any changes that fall into one of the "unacceptable"
       categories.  (For example, a fix for a crashing bug must not be
       included if it breaks binary compatibility.)

       It is not necessary to include every change meeting these criteria, and
       in general the focus should be on addressing security issues, crashing
       bugs, regressions and serious installation issues.  The temptation to
       include a plethora of minor changes that don't affect the installation
       or execution of perl (e.g. spelling corrections in documentation)
       should be resisted in order to reduce the overall risk of overlooking
       something.  The intention is to create maintenance releases which are
       both worthwhile and which users can have full confidence in the
       stability of.  (A secondary concern is to avoid burning out the maint-
       release manager or overwhelming other committers voting on changes to
       be included (see "Getting changes into a maint branch" below).)

       The following types of change may be considered acceptable, as long as
       they do not also fall into any of the "unacceptable" categories set out

       o   Patches that fix CVEs or security issues.  These changes should be
           passed using the security reporting mechanism rather than applied

       o   Patches that fix crashing bugs, assertion failures and memory
           corruption but which do not otherwise change perl's functionality
           or negatively impact performance.

       o   Patches that fix regressions in perl's behavior relative to
           previous releases, no matter how old the regression, since some
           people may upgrade from very old versions of perl to the latest

       o   Patches that fix bugs in features that were new in the
           corresponding 5.x.0 stable release.

       o   Patches that fix anything which prevents or seriously impacts the
           build or installation of perl.

       o   Portability fixes, such as changes to Configure and the files in
           the hints/ folder.

       o   Minimal patches that fix platform-specific test failures.

       o   Documentation updates that correct factual errors, explain
           significant bugs or deficiencies in the current implementation, or
           fix broken markup.

       o   Updates to dual-life modules should consist of minimal patches to
           fix crashing bugs or security issues (as above).  Any changes made
           to dual-life modules for which CPAN is canonical should be
           coordinated with the upstream author.

       The following types of change are NOT acceptable:

       o   Patches that break binary compatibility.  (Please talk to the
           steering council.)

       o   Patches that add or remove features.

       o   Patches that add new warnings or errors or deprecate features.

       o   Ports of Perl to a new platform, architecture or OS release that
           involve changes to the implementation.

       o   New versions of dual-life modules should NOT be imported into
           maint.  Those belong in the next stable series.

       If there is any question about whether a given patch might merit
       inclusion in a maint release, then it almost certainly should not be

   Getting changes into a maint branch
       Historically, only the single-person project manager cherry-picked
       changes from bleadperl into maintperl.  This has scaling problems.  At
       the same time, maintenance branches of stable versions of Perl need to
       be treated with great care.  To that end, as of Perl 5.12, we have a
       new process for maint branches.

       Any committer may cherry-pick any commit from blead to a maint branch
       by first adding an entry to the relevant voting file in the maint-votes
       branch announcing the commit as a candidate for back-porting, and then
       waiting for at least two other committers to add their votes in support
       of this (i.e. a total of at least three votes is required before a
       commit may be back-ported).

       Most of the work involved in both rounding up a suitable set of
       candidate commits and cherry-picking those for which three votes have
       been cast will be done by the maint branch release manager, but anyone
       else is free to add other proposals if they're keen to ensure certain
       fixes don't get overlooked or fear they already have been.

       Other voting mechanisms may also be used instead (e.g. sending mail to
       perl5-porters and at least two other committers responding to the list
       giving their assent), as long as the same number of votes is gathered
       in a transparent manner.  Specifically, proposals of which changes to
       cherry-pick must be visible to everyone on perl5-porters so that the
       views of everyone interested may be heard.

       It is not necessary for voting to be held on cherry-picking perldelta
       entries associated with changes that have already been cherry-picked,
       nor for the maint-release manager to obtain votes on changes required
       by the Porting/release_managers_guide.pod where such changes can be
       applied by the means of cherry-picking from blead.


   A Social Contract about Artistic Control
       What follows is a statement about artistic control, defined as the
       ability of authors of packages to guide the future of their code and
       maintain control over their work.  It is a recognition that authors
       should have control over their work, and that it is a responsibility of
       the rest of the Perl community to ensure that they retain this control.
       It is an attempt to document the standards to which we, as Perl
       developers, intend to hold ourselves.  It is an attempt to write down
       rough guidelines about the respect we owe each other as Perl

       This statement is not a legal contract.  This statement is not a legal
       document in any way, shape, or form.  Perl is distributed under the GNU
       Public License and under the Artistic License; those are the precise
       legal terms.  This statement isn't about the law or licenses.  It's
       about community, mutual respect, trust, and good-faith cooperation.

       We recognize that the Perl core, defined as the software distributed
       with the heart of Perl itself, is a joint project on the part of all of
       us.  From time to time, a script, module, or set of modules (hereafter
       referred to simply as a "module") will prove so widely useful and/or so
       integral to the correct functioning of Perl itself that it should be
       distributed with the Perl core.  This should never be done without the
       author's explicit consent, and a clear recognition on all parts that
       this means the module is being distributed under the same terms as Perl
       itself.  A module author should realize that inclusion of a module into
       the Perl core will necessarily mean some loss of control over it, since
       changes may occasionally have to be made on short notice or for
       consistency with the rest of Perl.

       Once a module has been included in the Perl core, however, everyone
       involved in maintaining Perl should be aware that the module is still
       the property of the original author unless the original author
       explicitly gives up their ownership of it.  In particular:

       o   The version of the module in the Perl core should still be
           considered the work of the original author.  All patches, bug
           reports, and so forth should be fed back to them.  Their
           development directions should be respected whenever possible.

       o   Patches may be applied by the steering council without the explicit
           cooperation of the module author if and only if they are very
           minor, time-critical in some fashion (such as urgent security
           fixes), or if the module author cannot be reached.  Those patches
           must still be given back to the author when possible, and if the
           author decides on an alternate fix in their version, that fix
           should be strongly preferred unless there is a serious problem with
           it.  Any changes not endorsed by the author should be marked as
           such, and the contributor of the change acknowledged.

       o   The version of the module distributed with Perl should, whenever
           possible, be the latest version of the module as distributed by the
           author (the latest non-beta version in the case of public Perl
           releases), although the steering council may hold off on upgrading
           the version of the module distributed with Perl to the latest
           version until the latest version has had sufficient testing.

       In other words, the author of a module should be considered to have
       final say on modifications to their module whenever possible (bearing
       in mind that it's expected that everyone involved will work together
       and arrive at reasonable compromises when there are disagreements).

       As a last resort, however:

       If the author's vision of the future of their module is sufficiently
       different from the vision of the steering council and perl5-porters as
       a whole so as to cause serious problems for Perl, the steering council
       may choose to formally fork the version of the module in the Perl core
       from the one maintained by the author.  This should not be done lightly
       and should always if at all possible be done only after direct input
       from Larry.  If this is done, it must then be made explicit in the
       module as distributed with the Perl core that it is a forked version
       and that while it is based on the original author's work, it is no
       longer maintained by them.  This must be noted in both the
       documentation and in the comments in the source of the module.

       Again, this should be a last resort only.  Ideally, this should never
       happen, and every possible effort at cooperation and compromise should
       be made before doing this.  If it does prove necessary to fork a module
       for the overall health of Perl, proper credit must be given to the
       original author in perpetuity and the decision should be constantly re-
       evaluated to see if a remerging of the two branches is possible down
       the road.

       In all dealings with contributed modules, everyone maintaining Perl
       should keep in mind that the code belongs to the original author, that
       they may not be on perl5-porters at any given time, and that a patch is
       not official unless it has been integrated into the author's copy of
       the module.  To aid with this, and with points #1, #2, and #3 above,
       contact information for the authors of all contributed modules should
       be kept with the Perl distribution.

       Finally, the Perl community as a whole recognizes that respect for
       ownership of code, respect for artistic control, proper credit, and
       active effort to prevent unintentional code skew or communication gaps
       is vital to the health of the community and Perl itself.  Members of a
       community should not normally have to resort to rules and laws to deal
       with each other, and this document, although it contains rules so as to
       be clear, is about an attitude and general approach.  The first step in
       any dispute should be open communication, respect for opposing views,
       and an attempt at a compromise.  In nearly every circumstance nothing
       more will be necessary, and certainly no more drastic measure should be
       used until every avenue of communication and discussion has failed.


       Perl's documentation is an important resource for our users. It's
       incredibly important for Perl's documentation to be reasonably coherent
       and to accurately reflect the current implementation.

       Just as P5P collectively maintains the codebase, we collectively
       maintain the documentation.  Writing a particular bit of documentation
       doesn't give an author control of the future of that documentation.  At
       the same time, just as source code changes should match the style of
       their surrounding blocks, so should documentation changes.

       Examples in documentation should be illustrative of the concept they're
       explaining.  Sometimes, the best way to show how a language feature
       works is with a small program the reader can run without modification.
       More often, examples will consist of a snippet of code containing only
       the "important" bits.  The definition of "important" varies from
       snippet to snippet.  Sometimes it's important to declare "use strict"
       and "use warnings", initialize all variables and fully catch every
       error condition.  More often than not, though, those things obscure the
       lesson the example was intended to teach.

       As Perl is developed by a global team of volunteers, our documentation
       often contains spellings which look funny to somebody.  Choice of
       American/British/Other spellings is left as an exercise for the author
       of each bit of documentation.  When patching documentation, try to
       emulate the documentation around you, rather than changing the existing

       In general, documentation should describe what Perl does "now" rather
       than what it used to do.  It's perfectly reasonable to include notes in
       documentation about how behaviour has changed from previous releases,
       but, with very few exceptions, documentation isn't "dual-life" -- it
       doesn't need to fully describe how all old versions used to work.


       The official forum for the development of perl is the perl5-porters
       mailing list, mentioned above, and its bugtracker at GitHub.  Posting
       to the list and the bugtracker is not a right: all participants in
       discussion are expected to adhere to a standard of conduct.

       o   Always be civil.

       o   Heed the moderators.

       Civility is simple: stick to the facts while avoiding demeaning
       remarks, belittling other individuals, sarcasm, or a presumption of bad
       faith. It is not enough to be factual.  You must also be civil.
       Responding in kind to incivility is not acceptable.  If you relay
       otherwise-unposted comments to the list from a third party, you take
       responsibility for the content of those comments, and you must
       therefore ensure that they are civil.

       While civility is required, kindness is encouraged; if you have any
       doubt about whether you are being civil, simply ask yourself, "Am I
       being kind?" and aspire to that.

       If the list moderators tell you that you are not being civil, carefully
       consider how your words have appeared before responding in any way.
       Were they kind?  You may protest, but repeated protest in the face of a
       repeatedly reaffirmed decision is not acceptable.  Repeatedly
       protesting about the moderators' decisions regarding a third party is
       also unacceptable, as is continuing to initiate off-list contact with
       the moderators about their decisions.

       Unacceptable behavior will result in a public and clearly identified
       warning.  A second instance of unacceptable behavior from the same
       individual will result in removal from the mailing list and GitHub
       issue tracker, for a period of one calendar month.  The rationale for
       this is to provide an opportunity for the person to change the way they

       After the time-limited ban has been lifted, a third instance of
       unacceptable behavior will result in a further public warning.  A
       fourth or subsequent instance will result in an indefinite ban.  The
       rationale is that, in the face of an apparent refusal to change
       behavior, we must protect other community members from future
       unacceptable actions.  The moderators may choose to lift an indefinite
       ban if the person in question affirms they will not transgress again.

       Removals, like warnings, are public.

       The list of moderators will be public knowledge.  At present, it is:
       Karen Etheridge, Neil Bowers, Nicholas Clark, Ricardo Signes, Todd


       "Social Contract about Contributed Modules" originally by Russ Allbery
       <> and the perl5-porters.

perl v5.34.0                      2021-05-04                   PERLPOLICY(1pm)

perl 5.34.0 - Generated Sat Feb 26 19:35:39 CST 2022
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