Determining minimum Perl version for new module

wanna_code_perl has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Determining minimum Perl version for new module by Your Mother (Archbishop) on Sep 12, 2019 at 01:47 UTC
This just came. up a few days ago: How to determine what code is limiting needed perl version for a module. I installed it to play around with it and it seems to work well though I’ve only tried it on a couple of things: Perl::MinimumVersion. Here’s some output from it suggesting that I’ve likely set the version much too high in some of my own code. `perlver lib/MuhCodes.pm ---------------------------------------------- \| file \| explicit \| syntax \| external \| \| ---------------------------------------------- \| \| lib/MuhCodes.pm \| v5.16.0 \| v5.8.0 \| n/a \| \| ---------------------------------------------- \| \| Minimum explicit version : v5.16.0. \| \| Minimum syntax version : v5.8.0. \| \| Minimum version of perl : v5.16.0. \| ----------------------------------------------` [download] Update: I agree with stevieb’s advice. Leave it out unless you actually need it to block a test runner or something from trying a Perl that’s too low.	[reply] [d/l]
Re: Determining minimum Perl version for new module by choroba (Cardinal) on Sep 12, 2019 at 09:09 UTC
My Syntax::Construct provides another viewpoint: if you know what features were introduced, you don't have to remember in which version it happened. Just list the features you use in the code and the module will require the appropriate version. It will also tell a user why exactly their version can't be used if it's too old. `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l]
Re: Determining minimum Perl version for new module by haukex (Archbishop) on Sep 12, 2019 at 18:14 UTC
Personally, the lowest I go is 5.6, because that introduced: Three-argument open Lexical filehandles Lexical warnings our omitting `->` between dereferences However, sometimes I require 5.8, because that improved the Unicode support and had some changes to I/O, i.e. PerlIO (plus it has safe signals). As for what the lowest version you should support for a new module, IMHO: I think good reasons to support the versions above might be: because your module is providing some feature that users of the above Perls might not otherwise have, or because you happen to know that some people who are stuck on 5.6 and 5.8 might need your module. Otherwise, I'd suggest starting with 5.10, since that introduced `//` and several regex improvements, such as named capture buffers. Newer versions of course have nice features, just some examples: 5.12 changed `length undef` to return `undef`, without throwing a warning 5.14 introduced `s///r` and `package NAME BLOCK` 5.16 introduced `__SUB__` and fc ... and so on. However, personally I find that for libraries I release, I'm ok with sticking to the 5.10 feature set (excluding smart matching, of course). For scripts that I write, I'll often go with 5.26 and up. Update: Added an item to the list, thanks Discipulus!	[reply] [d/l] [select]
Re: Determining minimum Perl version for new module by stevieb (Canon) on Sep 12, 2019 at 00:42 UTC
You're the only person who has made decisions on what features of Perl you require. That directly relates to what version of Perl your software needs. If you go non-core in your prerequisites, then that software will take care of the requisite perl you need (generally). Leave the requirement blank, unless you need a specific version. If you do require something specific, ensure you put it both in the file you're needing it, as well as in your `Makefile.PL` or equivalent. Personally, I would say no statement at all, but if anything, `5.10` "for a reasonable start", only for the defined-or operator.	[reply] [d/l] [select]
Re^2: Determining minimum Perl version for new module by wanna_code_perl (Friar) on Sep 12, 2019 at 01:07 UTC
You're the only person who has made decisions on what features of Perl you require. Agree! But sometimes a little outside discussion can help refine those decisions, so thank you for entertaining said discussion. :-)	[reply]
Re^3: Determining minimum Perl version for new module by stevieb (Canon) on Sep 12, 2019 at 01:57 UTC
If that's the case, I say require `5.10`. For me personally, it'd cover my `5.8` standard, and any requirement above that. The CPAN Testers will ensure things work correctly against your required version of Perl, as should your local testing. If not, might I suggest the following: test against numerous versions of `perl` via perlbrew or berrybrew ensure that your software works against any custom libraries you have locally verify that any local security validation is either workable or bypassed in testing document and criticize any client data that you've tested against, sanitize after digesting it, and request client feedback on its handling Beyond that, just have numerous test platforms to run against that you can reset on every test run. There's no way to validate everything every time, so use your best judgement. If your platform is useful and there's an issue found, make sure you have very accessible contact information.	[reply] [d/l] [select]
Re: Determining minimum Perl version for new module by jcb (Parson) on Sep 12, 2019 at 19:17 UTC
I see backwards compatibility as a major pillar of the Perl community, so I would suggest aiming to support whatever version provides the features your API needs, within reason. For example, I am currently working on a WARC library for Perl and the API uses tied lexical filehandles — and there were bugs in 5.8.0 that resulted in leaking lexical filehandles, so 5.8.1 is the minimum for my project, even though some versions of 5.6 might be able to run my code. That said, there is still at least one 5.8.5 smoker out there, (and my non-broken tests have passed on it) so as a practical matter I would be more inclined to bump the required version rather than work around bugs in perl releases even more ancient than that. My philosophy is generally to let older versions run the tests and see if I get failure reports, but to go ahead and exclude versions known to have bugs that would cause disaster if the code were put into production. I am up to "alpha-5" as I call v0.0.0_5 currently. I follow release early, release often, as long as the tests exist and pass: the very first "alpha-1" release had no actual code, just empty subs and stub unit tests to ensure that the modules parse OK and verify the embedded POD. Each subsequent release has been a step along the way to building the library, while rolling in bug fixes for previously-failing tests. The CPAN smokers seem to all run various Unix-like systems but are still an impressive variety of configurations. If your distribution has a version with an underscore instead of a dot ahead of the last number, the smokers will test it but it will only be installed for users if specifically requested.	[reply]
Re^2: Determining minimum Perl version for new module by hippo (Archbishop) on Sep 13, 2019 at 08:57 UTC
The CPAN smokers seem to all run various Unix-like systems My modest stable of modules has seen tests from some MSWin32 smokers recently. Previously there were also tests coming from Haiku which I wouldn't consider Unix-like although no doubt it could be argued as such. It would be nice to see even greater diversity of course but it is what it is.	[reply]
Re: Determining minimum Perl version for new module by Anonymous Monk on Sep 12, 2019 at 19:44 UTC
My opinion would be: If it's toolchain, support 5.8.1. Otherwise support 5.10.1 if reasonable, or 5.14.0 to be able to use keywords. 5.10.1 is by far the biggest user base due to RHEL6, but it's shrinking. There is a useful chart maintained of versions reported by cpanm, just remember it's a subsection of the community: http://cpanmetadb.plackperl.org/versions/ -Grinnz	[reply]
Re: Determining minimum Perl version for new module by Anonymous Monk on Sep 12, 2019 at 02:17 UTC
Are there recent stats or census data on Perl versions in use in the wild? One way to see what people are supporting is to watch the CPAN. Most modules have a `use VERSION` or `use feature 'VERSION'` line. The MetaCPAN API provides a lot of information about modules but I couldn't find anything about the supported Perl version (which is found in the source code): https://metacpan.org/feed/recent https://metacpan.org/recent?f=n https://metacpan.org/favorite/leaderboard Whip up a bot that checks what versions of Perl are supported by which CPAN upload/new dist/fav/etc and plot a graph of CPAN's most supported Perl versions so you can upload it to cool uses?	[reply]
Re^2: Determining minimum Perl version for new module by Corion (Patriarch) on Sep 12, 2019 at 07:34 UTC
Another good measure is to look at what version of Perl the long term editions of popular Linux distributions and Apple distribute (and thus, support). Currently, I think these are RHEL 6 - Perl 5.10, EOL 2020 RHEL 7 - Perl 5.18 (I think?), Perl 5.24 available as package, EOL 2024 Debian 9 - Perl 5.18, EOL 2022 Debian 10 - Perl 5.28, EOL 2022 Ubuntu Xenial - Perl 5.20 OSX (Yosemite upwards) - Perl 5.18 Also see Which version of perl comes with ...?.	[reply]
Re^3: Determining minimum Perl version for new module by hippo (Archbishop) on Sep 12, 2019 at 08:15 UTC
RHEL 7 - Perl 5.18 (I think?) Actually it's only 5.16.3 on RHEL7. RHEL8 has 5.26.3. That's quite a jump but then it has been almost 5 years between their major releases.	[reply]
Re^4: Determining minimum Perl version for new module by Tux (Canon) on Sep 12, 2019 at 08:43 UTC
Re^3: Determining minimum Perl version for new module by Tux (Canon) on Sep 12, 2019 at 08:41 UTC
On distrowatch you can dig through the Linux distributions to make a list of which distro comes with what perl version. (I try to keep a CSV list up-to-date for System::Info). A summary: 5.6 54 # .0: 16, .1: 38 5.8 372 # .0: 39, .1: 7, .2: 11, .3: 11, .4: 42, .5: 26, .6: 21, .7 +: 29, .8:184, .9: 2 5.10 270 # .0:105, .1:165 5.12 110 # .1: 10, .2: 24, .3: 36, .4: 40 5.14 166 # .0: 3, .1: 4, .2:156, .3: 1, .4: 2 5.16 59 # .0: 1, .1: 15, .2: 7, .3: 36 5.18 119 # .0: 8, .1: 31, .2: 77, .4: 3 5.20 145 # .0: 15, .1: 23, .2: 98, .3: 9 5.22 128 # .0: 12, .1: 74, .2: 36, .3: 6 5.24 137 # .0: 19, .1: 95, .2: 3, .3: 19, .4: 1 5.26 135 # .0: 19, .1: 72, .2: 41, .3: 3 5.28 117 # .0: 23, .1: 80, .2: 14 5.30 28 # .0: 28 [download] If I limit that list to dists that got a release since 2017-01-01, I get: `5.8 2 # .8: 2 5.10 10 # .1: 10 5.12 4 # .3: 4 5.14 7 # .2: 6, .3: 1 5.16 15 # .3: 15 5.18 11 # .0: 2, .1: 1, .2: 8 5.20 44 # .0: 2, .2: 38, .3: 4 5.22 60 # .0: 1, .1: 44, .2: 9, .3: 6 5.24 121 # .0: 8, .1: 90, .2: 3, .3: 19, .4: 1 5.26 135 # .0: 19, .1: 72, .2: 41, .3: 3 5.28 117 # .0: 23, .1: 80, .2: 14 5.30 28 # .0: 28` [download] and limiting to 2018 and 2019: `5.8 1 # .8: 1 5.10 4 # .1: 4 5.12 3 # .3: 3 5.14 5 # .2: 4, .3: 1 5.16 12 # .3: 12 5.18 4 # .0: 1, .2: 3 5.20 12 # .0: 1, .2: 10, .3: 1 5.22 30 # .1: 22, .2: 5, .3: 3 5.24 71 # .0: 2, .1: 54, .3: 14, .4: 1 5.26 108 # .0: 2, .1: 62, .2: 41, .3: 3 5.28 117 # .0: 23, .1: 80, .2: 14 5.30 28 # .0: 28` [download] With just one dist (openwall-3.1, which is the most recent openwall distributeded with perl on 2018-07-03) shipping with perl-5.8.8, I'd say having a minimum of 5.10.1 is a very safe choice. If you however really want to use a feature like `s{}{}r`, perlver tells me you'd need 5.14.0. Enjoy, Have FUN! H.Merijn	[reply] [d/l] [select]