PERLPOLICY(1) Perl Programmers Reference Guide PERLPOLICY(1)
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.
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
committers.
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.
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.
5.36.x and earlier are now out of support. As of the release of
5.42.0, we will "officially" end support for Perl 5.38.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. See "SECURITY VULNERABILITY CONTACT
INFORMATION" in perlsec for details on how 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 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.
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.
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.
deprecated
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.
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 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.
removed
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.
MAINTENANCE BRANCHES
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
below:
• Patches that fix CVEs or security issues. These changes should be
passed using the security reporting mechanism rather than applied
directly; see "SECURITY VULNERABILITY CONTACT INFORMATION" in
perlsec.
• Patches that fix crashing bugs, assertion failures and memory
corruption but which do not otherwise change perl's functionality or
negatively impact performance.
• 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 version.
• Patches that fix bugs in features that were new in the corresponding
5.x.0 stable release.
• Patches that fix anything which prevents or seriously impacts the
build or installation of perl.
• Portability fixes, such as changes to Configure and the files in the
hints/ folder.
• Minimal patches that fix platform-specific test failures.
• Documentation updates that correct factual errors, explain
significant bugs or deficiencies in the current implementation, or
fix broken markup.
• 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:
• Patches that break binary compatibility. (Please talk to the
steering council.)
• Patches that add or remove features.
• Patches that add new warnings or errors or deprecate features.
• Ports of Perl to a new platform, architecture or OS release that
involve changes to the implementation.
• 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
included.
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.
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 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.
• 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.
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.
STANDARDS OF CONDUCT
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.
• Always be civil.
• 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 act.
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
Rinaldo.
CREDITS
"Social Contract about Contributed Modules" originally by Russ Allbery
<rra@stanford.edu> and the perl5-porters.
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