Provided by: perl-doc_5.18.2-2ubuntu1.7_all 
NAME
perlpolicy - Various and sundry policies and commitments related to the Perl core
DESCRIPTION
This document is the master document which records all written policies about how the Perl 5 Porters
collectively develop and maintain the Perl core.
GOVERNANCE
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.
MAINTENANCE AND SUPPORT
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
<perl5-security-report@perl.org> to begin that process.
BACKWARD COMPATIBILITY AND DEPRECATION
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 Perl.
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.
Terminology
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.
experimental
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.
deprecated
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.
discouraged
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 core.
removed
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.
MAINTENANCE BRANCHES
• 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
perl5-security-report@perl.org 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 committers.)
CONTRIBUTED MODULES
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 developers.
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.
DOCUMENTATION
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 prose.
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.
CREDITS
"Social Contract about Contributed Modules" originally by Russ Allbery <rra@stanford.edu> and the
perl5-porters.
perl v5.18.2 2013-11-04 PERLPOLICY(1)