http://qs321.pair.com?node_id=845207


in reply to Variable matching on a regex

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my $data = '123 456 789 987 654 321';

my @results;
$data =~ /(\d+\s*(?{push @results, $1 if defined $1}))+$/;
push @results, $1;

print Dumper(@results);

[download]

Just messing around seeing what could be done. not really sure why the last match doesn't get included or why the first one is undef, but i think they are probably related. Perhaps i'm actually pushing the last match not the current match, in fact thats almost certainly whats happening, anyone know how to reference the current match in a code block?


___________
Eric Hodges

Replies are listed 'Best First'.
Re^2: Variable matching on a regex
by almut (Canon) on Jun 17, 2010 at 14:47 UTC
    not really sure why the last match doesn't get included or why the first one is undef

    I think the capture group needs to be closed before being able to push its value.  This would work without further ado: 

    $data =~ /^(?:(\d+)\s*(?{ push @results, $^N }))+$/;

    [download]


    (Update)  P.S.: if you use this construct in a loop like in the OP's case, you need to declare the lexical @results outside of the loop for it to work properly.  I.e., while this is ok: 

    my @results;
while (<DATA>) {
    @results = ();
    /^(?:(\d+)\s*(?{ push @results, $^N }))+$/;
    print "line $.: ", join('-', @results), "\n";
}

__DATA__
1 2 3 4 5
2 3 4 5 6
3 4 5 6 7

    [download]

    output: 

    line 1: 1-2-3-4-5
line 2: 2-3-4-5-6
line 3: 3-4-5-6-7

    [download]

    the following would work only once: 

    while (<DATA>) {
    my @results;
    /^(?:(\d+)\s*(?{ push @results, $^N }))+$/;
    print "line $.: ", join('-', @results), "\n";
}

    [download]

    output: 

    line 1: 1-2-3-4-5
line 2: 
line 3:

    [download]


    (Fixed /^(:?... typo — thanks eric256! )

[reply]
[d/l]
[select]

      Looks like minor typo at the start of the regex, but it works!

      $data =~ /(?:(\d+)\s*(?{push @results, $^N}))+$/;

      ___________
      Eric Hodges
[reply]
[d/l]

In Section Seekers of Perl Wisdom