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

Is there an easy way to find out when a feature or keyword was introduced to Perl?
In other words, which version introduced it...

I have a module that uses pos, a keyword I infrequently use. How can I find out when this, or any other keyword, was introduced so I can set the minimum required Perl version?

Obviously I could go through each delta until I find it but that seems rather tedious...

  • Comment on Finding when a feature or keyword was introduced

Replies are listed 'Best First'.
Perl named operators and builtin subs introduced since 5.6
by ikegami (Patriarch) on Sep 27, 2023 at 06:18 UTC

    Perl named operators and builtin subs introduced since 5.6

    NameAvailabilityExperimentalIn CORE::Enabling
    pragma    		Enabling
    feature set
    __CLASS__Since 5.40—Since 5.40use feature qw( class );—
    __SUB__Since 5.16—Since 5.16use feature qw( current_sub );5.16 and up
    ADJUSTSince 5.38Since 5.40Since 5.38use feature qw( class );—
    allSince 5.42Since 5.42Since 5.42use feature qw( keyword_all );—
    anySince 5.42Since 5.42Since 5.42use feature qw( keyword_any );—
    blessedSince 5.36From 5.36 until 5.40—use builtin qw( blessed );5.40 and up
    breakFrom 5.10Since 5.16[1] until 5.38
    Deprecated from 5.38 until 5.42    		Since 5.16use feature qw( switch );From 5.10
    up to 5.36
    catchSince 5.34From 5.34 until 5.40Since 5.34use feature qw( try );5.40 and up
    ceilSince 5.36From 5.36 until 5.40—use builtin qw( ceil );5.40 and up
    classSince 5.38Since 5.38Since 5.38use feature qw( class );—
    continueFrom 5.10Since 5.16[1] until 5.38
    Deprecated from 5.38 until 5.42    		Since 5.16use feature qw( switch );From 5.10
    up to 5.36
    created_as_numberSince 5.36Since 5.36—use builtin qw( created_as_number );—
    created_as_stringSince 5.36Since 5.36—use builtin qw( created_as_string );—
    defaultFrom 5.10Since 5.16[1] until 5.38
    Deprecated from 5.38 until 5.42    		Since 5.16use feature qw( switch );From 5.10
    up to 5.36
    deferSince 5.36Since 5.36Since 5.36use feature qw( defer );5.40 and up
    export_lexicallySince 5.38Since 5.38—use builtin qw( export_lexically );—
    falseSince 5.36From 5.36 until 5.40—use builtin qw( false );—
    fc Since 5.16—Since 5.16use feature qw( fc );5.16 and up
    fieldSince 5.38Since 5.38Since 5.38use feature qw( class );—
    floorSince 5.36From 5.36 until 5.40—use builtin qw( floor );5.40 and up
    finallySince 5.36Since 5.36Since 5.36use feature qw( try );5.40 and up
    givenFrom 5.10Since 5.16[1] until 5.38
    Deprecated from 5.38 until 5.42    		Since 5.16use feature qw( switch );From 5.10
    up to 5.36
    indexedSince 5.36From 5.36 until 5.40—use builtin qw( indexed );5.40 and up
    infSince 5.40Since 5.40—use builtin qw( inf );—
    is_boolSince 5.36Since 5.36—use builtin qw( is_bool );—
    is_taintedSince 5.38From 5.38 until 5.40—use builtin qw( is_tainted );5.40 and up
    is_weakSince 5.36From 5.36 until 5.40—use builtin qw( is_weak );5.40 and up
    isaSince 5.32From 5.32 until 5.34Since 5.32use feature qw( isa );5.36 and up
    load_moduleSince 5.40Since 5.40—use builtin qw( load_module );—
    methodSince 5.38Since 5.38Since 5.38use feature qw( class );—
    nanSince 5.40Since 5.40—use builtin qw( nan );—
    refaddrSince 5.36From 5.36 until 5.40—use builtin qw( refaddr );5.40 and up
    reftypeSince 5.36From 5.36 until 5.40—use builtin qw( reftype );5.40 and up
    saySince 5.10—Since 5.16use feature qw( say );5.10 and up
    stateSince 5.10—Since 5.16use feature qw( state );5.10 and up
    stringifySince 5.40Since 5.40—use builtin qw( stringify );—
    trimSince 5.36From 5.36 until 5.40—use builtin qw( trim );5.40 and up
    trueSince 5.36From 5.36 until 5.40—use builtin qw( true );5.40 and up
    trySince 5.34From 5.34 until 5.40Since 5.34use feature qw( try );5.40 and up
    unweakenSince 5.36From 5.36 until 5.40—use builtin qw( unweaken );5.40 and up
    weakenSince 5.36From 5.36 until 5.40—use builtin qw( weaken );5.40 and up
    whenFrom 5.10Since 5.16[1] until 5.38
    Deprecated from 5.38 until 5.42    		Since 5.16use feature qw( switch );From 5.10
    up to 5.36
     
    builtin::blessedSince 5.36From 5.36 until 5.40—Always available
    builtin::ceilSince 5.36From 5.36 until 5.40—Always available
    builtin::created_as_numberSince 5.36Since 5.36—Always available
    builtin::created_as_stringSince 5.36Since 5.36—Always available
    builtin::export_lexicallySince 5.38Since 5.38—Always available
    builtin::falseSince 5.36From 5.36 until 5.40—Always available
    builtin::floorSince 5.36From 5.36 until 5.40—Always available
    builtin::indexedSince 5.36From 5.36 until 5.40—Always available
    builtin::infSince 5.40Since 5.40—Always available
    builtin::is_boolSince 5.36Since 5.36—Always available
    builtin::is_taintedSince 5.38From 5.38 until 5.40—Always available
    builtin::is_weakSince 5.36From 5.36 until 5.40—Always available
    builtin::load_moduleSince 5.40Since 5.40—Always available
    builtin::nanSince 5.40Since 5.40—Always available
    builtin::refaddrSince 5.36From 5.36 until 5.40—Always available
    builtin::reftypeSince 5.36From 5.36 until 5.40—Always available
    builtin::stringifySince 5.40Since 5.40—Always available
    builtin::trimSince 5.36From 5.36 until 5.40—Always available
    builtin::trueSince 5.36From 5.36 until 5.40—Always available
    builtin::unweakenSince 5.36From 5.36 until 5.40—Always available
    builtin::weakenSince 5.36From 5.36 until 5.40—Always available
     
    utf8::decodeSince 5.8——Always available
    utf8::downgradeSince 5.8——Always available
    utf8::encodeSince 5.8——Always available
    utf8::is_utf8Since 5.8.1——Always available
    utf8::native_to_unicodeSince 5.8[2]——Always available
    utf8::unicode_to_nativeSince 5.8[2]——Always available
    utf8::upgradeSince 5.8——Always available
    utf8::validSince 5.8——Always available

    Notes

    • Current as of 5.42.
    • Perl provides other builtin subs which are meant to be used as methods, which aren't documented to be available at all times, or which aren't documented at all. (These are found in in constant::, Internals::, PerlIO::, re::, Tie::Hash::NamedCapture, UNIVERSAL:: and version::). These are deliberately omitted.
    • The existence of dev versions is ignored.
    • "Until 5.xx" and "up to 5.xx" are exclusive, meaning they don't include 5.xx.

    Footnotes

    1. Experimental warnings were only added in 5.18, but the switch feature was documented to be experimental since 5.16.
    2. While utf8::native_to_unicode and utf8::unicode_to_native have only been documented since 5.22, they've been available since 5.8.

    Updates

    1. Added the keywords from the class feature.
    2. Fixed versions for defer.
    3. Fixed versions for finally.
    4. Added availability in CORE::.
    5. is_tainted, export_lexically, builtin::is_tainted and builtin::export_lexically were missing.
    6. Updated for 5.40.
    7. Updated for 5.42.
[reply]
[d/l]
[select]

      Good table, but maybe it doesn't need to list everything from builtin twice? Better to just make a note that they can always be used by their fully-qualified name or imported lexically.

      Hire me at Toby Ink Ltd or Join my OnlyFans
[reply]
[d/l]
[reply]
[d/l]
[select]

        I've mistakenly said the feature became experimental in 5.18 in the past too. But while the experimental warnings were added in 5.18, it was flagged as experimental in 5.16.

        Quote 5.16's perlsyn,

        you can say use feature "switch"; to enable an experimental switch feature.

        Also,

        Under the "switch" feature, Perl gains the experimental keywords given, when, default, continue, and break.

        Added break, default and continue to the table.

[reply]
[d/l]
[select]

      Great table - thanks :)

      I would have expected to see class in there as that's new in 5.36 isn't it? I've not used it or investigated it as 5.32 is the latest version I have.

[reply]
[d/l]

        I would have expected to see class in there as that's new in 5.36 isn't it?

        Good point. I just checked perlclass, and I see keywords: class, field and method. Not sure if attributes :isa and :param qualify.

[reply]
[d/l]
[select]

        5.38. Overlooked. Fixed. Thanks.

[reply]

      Great table, thanks! Is there any way to find out when features other than keywords were added? I'm currently trying to find (1) when ref() began returning 'Regexp' and (2) when class 'Regexp' was added, if that was more recent than (1). Both ref() and Scalar::Util::blessed() return 'Regexp' as of v5.20.2. The referenced 5.38 delta page contains a link to select earlier versions, but it doesn't seem to work; a "raptor not found" error is displayed.

[reply]
        I collect some non-features in Syntax::Construct, but Regexp is not one of them (I might add it, though).

        map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]
[reply]
[d/l]

        A quick perusal through the docs for ref for historical versions of Perl suggests that the Regexp class started being reported in 5.8.9 but this is not mentioned in the 5.8.9 delta AFAICS. Nowadays that really ought to be so long ago that it doesn't matter anyway.

        🦛

[reply]

        It's been that way since at least 5.8.9. ("t" means threaded. Ignore that.) 

        $ for v in 5.8.9 5.10t 5.12t 5.14t 5.16t 5.18t 5.20t; do
   echo $v
   $v/bin/perl -le'print ref( qr/x/ )'
done
5.8.9
Regexp
5.10t
Regexp
5.12t
Regexp
5.14t
Regexp
5.16t
Regexp
5.18t
Regexp
5.20t
Regexp

        [download]
[reply]
[d/l]

      Updated parent for 5.42.

[reply]
Re: Finding when a feature or keyword was introduced
by SankoR (Prior) on Sep 26, 2023 at 17:57 UTC
[reply]
[d/l]
Re: Finding when a feature or keyword was introduced
by choroba (Cardinal) on Sep 26, 2023 at 18:00 UTC
    Regarding features, the documentation of feature lists the minimal Perl version for each feature.

    Regarding keywords, the ones not covered by features (i.e. everything but fc and say) are as old as I remember, so probably pre-5.6. There's no need to bother with so ancient versions.

    There are some things that were introduced over the years that weren't mentioned in the deltas or they were but the required version isn't mentioned in their documentation. That's why I created Syntax::Construct.

    Update: Reformulated. fc and say are examples of keywords covered by features.

    map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]
[reply]
[d/l]
[select]

      say is enabled with use v5.10 which implies it was introduced in that version.

      Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond
[reply]
[d/l]
[select]

      It doesn't list the versions for try (5.34) and defer (5.38) features. Both are still experimental as of 5.38.

[reply]
Re: Finding when a feature or keyword was introduced (perlver)
by Anonymous Monk on Sep 27, 2023 at 09:41 UTC
[reply]
      Perl::MinimumVersion Find a minimum required version of perl for Perl code

      WoW!!!
      Good find - thanks for sharing...

      Frok the documentation - Future plans are to also add support for tracing module dependencies

      It will be an essential tool as and when that comes to pass. I always struggle to know which version of modules to declare as necessary.

[reply]

        I don't think that means what you think it does. I read it as meaning that it will be extended to report the minimum perl version required by the modules on which the originally examined code depends. ie. it will do the same checks but descend recursively into the dependency tree.

        🦛

[reply]
Re: Finding when a feature or keyword was introduced
by ikegami (Patriarch) on Sep 27, 2023 at 05:35 UTC

    I don't believe any named operators ("functions") have been added since 5.6, except 1) those that need a pragma to enable, and 2) those that are in a namespace other than main::.

[reply]

Back to Seekers of Perl Wisdom