Fellow Monks,

I seek your wisdom: A recent node (Re: No tools? Use Perl?!) got me wondering: Is there a difference between these three regexes that I am missing, primarily in terms of what they match? In particular I'm interested in the first two - I understand the first and third regexes, but am not an expert on look-arounds.

  1. /<(.*?)>/s
  2. /<((?:(?!>).)*)>/s
  3. /<([^>]*)>/s

I have yet to find a difference - I am not sure if there even is one - but I'm probably not being creative enough in my test cases...

#!/usr/bin/env perl
use warnings;
use strict;
use Test::More;

#use re 'debug';
sub testre (_) {
    my $txt = shift;
    my @m1 = $txt =~ /<(.*?)>/sg;
    my @m2 = $txt =~ /<((?:(?!>).)*)>/sg;
    my @m3 = $txt =~ /<([^>]*)>/sg;
    is_deeply \@m1, \@m2, "$txt => (@m1) = (@m2)";
    is_deeply \@m1, \@m3, "$txt => (@m1) = (@m3)";
}
testre for (
    "<", "<<", "<<<", ">", ">>", ">>>",
    "<<<>", "<<>", "<>", "<>>", "<>>>",
    "<<>>", "<<<>>>",
    "<><>",  "<><><>", "<><<><>", "<><>><>",
    "a<b>c", "a<b>>c", "a<b>>>c", "a<<b>c", "a<<<b>c",
    "a<<b>>c", "a<<<b>>>c",
    "a<b>c<d>e",  "a<b>c<d>e<f>g",
    "a<b>c<<e>f<g>h", "a<b>c<d>>e<f>g",
    "a<b>c<e<f>g<h>i", "a<b>c<d>e>f<g>h",
    "<\n>\n", "<\n<\n>\n>\n", "<\n>\n<\n>\n",
);
done_testing;

[download]

Regards,
-- Hauke D

In reply to Difference between these regexes by haukex

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