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

       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.

       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 Perl 6, while
       Perl 5 is shepherded by a "pumpking", a porter 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), the Executive branch (the
       -pumpking), 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.

       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:

       ·   We "officially" support the two most recent stable release series.
	   5.12.x and earlier are now out of support.  As of the release of
	   5.18.0, we will "officially" end support for Perl 5.14.x, other
	   than providing security updates as described below.

       ·   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.

       ·   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.

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

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

       ·   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.  Contact us at
	   <> 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 a given language feature's continued
       inclusion in the language will cause significant harm to the language
       or prevent us from making needed changes to the runtime, then it may be
       considered for deprecation.

       Any language change which breaks backward-compatibility should be able
       to be enabled or disabled lexically.  Unless code at a given scope
       declares that it wants the new behavior, that new behavior should be
       disabled.  Which backward-incompatible changes are controlled
       implicitly by a 'use v5.x.y' is a decision which should be made by the
       pumpking in consultation with the community.

       When a backward-incompatible change can't be toggled lexically, the
       decision to change the language must be considered very, very
       carefully.  If it's possible to move the old syntax or semantics out of
       the core language and into XS-land, that XS module should be enabled by
       default unless the user declares that they want a newer revision of

       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.

       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.

	   If something in the Perl core is marked as deprecated, we may
	   remove it from the core in the next stable release series, though
	   we may not. 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 candidates for removal in the next
	   major release series, but we may later deprecate them if they're
	   found to stand in the way of a significant improvement to the Perl

	   Once a feature, construct or module has been marked as deprecated
	   for a stable release cycle, 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 maint should contain as few changes as possible.
	   If there is any question about whether a given patch might merit
	   inclusion in a maint release, then it almost certainly should not
	   be included.

       ·   Portability fixes, such as changes to Configure and the files in
	   hints/ are acceptable. Ports of Perl to a new platform,
	   architecture or OS release that involve changes to the
	   implementation are NOT acceptable.

       ·   Acceptable documentation updates are those that correct factual
	   errors, explain significant bugs or deficiencies in the current
	   implementation, or fix broken markup.

       ·   Patches that add new warnings or errors or deprecate features are
	   not acceptable.

       ·   Patches that fix crashing bugs that do not otherwise change Perl's
	   functionality or negatively impact performance are acceptable.

       ·   Patches that fix CVEs or security issues are acceptable, but should
	   be run through the mailing list
	   rather than applied directly.

       ·   Patches that fix regressions in perl's behavior relative to
	   previous releases are acceptable.

       ·   Updates to dual-life modules should consist of minimal patches to
	   fix crashing or security issues (as above).

       ·   Minimal patches that fix platform-specific test failures or
	   installation issues are acceptable. When these changes are made to
	   dual-life modules for which CPAN is canonical, any changes should
	   be coordinated with the upstream author.

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

       ·   Patches that add or remove features are not acceptable.

       ·   Patches that break binary compatibility are not acceptable.
	   (Please talk to a pumpking.)

   Getting changes into a maint branch
       Historically, only the pumpking 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
       if they send mail to perl5-porters announcing their intent to cherry-
       pick a specific commit along with a rationale for doing so and at least
       two other committers respond to the list giving their assent. (This
       policy applies to current and former pumpkings, as well as other

   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:

       ·   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.

       ·   Patches may be applied by the pumpkin holder 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.

       ·   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 pumpkin holder 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 pumpkin holder and perl5-porters as a
       whole so as to cause serious problems for Perl, the pumpkin holder 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.

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

perl v5.18.2			  2013-11-04		     PERLPOLICY(1perl)

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