http://www.perlmonks.org?node_id=1179958


in reply to Re^4: Feature Idea: qr//e
in thread Feature Idea: qr//e (updated with solutions)

It works only for some of the modifiers: 
my $regex = qre{ join '|', qw/foo bar/ }m;

[download]

Returns: 

Global symbol "$regex" requires explicit package name at ./1.pl line 1
+1.
Execution of ./1.pl aborted due to compilation errors.

[download]

Similarly, s yields 

Global symbol "$regex" requires explicit package name at ./1.pl line 1
+1.
syntax error at ./1.pl line 14, at EOF
  (Might be a runaway multi-line ;; string starting on line 11)
Execution of ./1.pl aborted due to compilation errors.

[download]
($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

[download]

Replies are listed 'Best First'.
Re^6: Feature Idea: qr//e
by TheDamian (Vicar) on Jan 20, 2017 at 19:54 UTC

    ++choroba

    You're quite right: not a good tweak when it's not 100% applicable.

    Of course, you could still write: 

    my $regex = qre{ join '|', qw/foo bar/ }m =>;

    [download]
    but that's probably just adding insult to injury.

    And, yes, I was indeed caught out by this because I no longer even think about the m or s modifiers.
    Especially now that I can add a standard: 

    use re '/xms';

    [download]
    at the top of every Perl file. ;-)

    Damian

[reply]
[d/l]
[select]
Re^6: Feature Idea: qr//e
by haukex (Archbishop) on Jan 21, 2017 at 10:10 UTC

    Hi choroba,

    Hm, the * prototype is a really cool idea, too bad about that... here's a less elegant workaround (also incorporates AnomalousMonk's suggestion). As far as I can tell, for single letter modifiers it's only m and s that cause a problem, the others (/ixpodualn) are fine, and multi-letter modifiers are fine as far as they don't clash with any other subs (like main, min, or sum) or operators (like and, although that's not a valid combination of modifiers). With the letters "msixpodualn" you can actually spell a lot of words :-)

    use List::Util qw/min sum/;
sub qre (&;*) {
    my $re = shift->();
    eval 'qr/$re/'.(@_ ? lc shift : '') || die $@
}

say qre{ join '|', qw/foo bar/ }M;
say qre{ join '|', qw/foo bar/ }msx;
say qre{ join '|', qw/foo bar/ }Min;
say qre{ join '|', qw/foo bar/ }Sum;

__END__

(?^m:foo|bar)
(?^msx:foo|bar)
(?^min:foo|bar)
(?^ums:foo|bar)

    [download]

    Regards,
    -- Hauke D

[reply]
[d/l]
[select]
Re^6: Feature Idea: qr//e
by AnomalousMonk (Archbishop) on Jan 19, 2017 at 23:25 UTC

    Oops...

    Well, qr//s should always be written with a standard /xms tail anyway, so 

    c:\@Work\Perl>perl -wMstrict -le
"sub qre (&;*) {
   my $re = shift->();
   return eval 'qr/$re/xms' . (@_ ? shift : '') or die $@;
   }
 ;;
 my $regex = qre{ join '|', qw/foo bar/ }i;
 print $regex;
"
(?msix:foo|bar)

    [download]
    :-))

    Give a man a fish:  <%-{-{-{-<

[reply]
[d/l]
[select]
Re^6: Feature Idea: qr//e
by LanX (Saint) on Jan 20, 2017 at 12:38 UTC
    Most probably the parser gets confused because m and s are builtin commands on their own and can't be bare words.

    In other words

    sub m {} should be illegal.

    Cheers Rolf
    (addicted to the Perl Programming Language and ☆☆☆☆ :)
    Je suis Charlie!

[reply]
[d/l]
[reply]
        Well it's a parsing problem, if you manage to enter a subroutine named s into the stash you can certainly call it with &s (which is not a bare word anymore)

        Can't test at the moment, and Perl's parser is known to be complicated. :)

        (I remember that CGI renamed tr to TR for this reason)

        Cheers Rolf
        (addicted to the Perl Programming Language and ☆☆☆☆ :)
        Je suis Charlie!

[reply]

In Section Seekers of Perl Wisdom