in reply to Re: "Not containing something" in substitution
in thread "Not containing something" in substitution

Neat RegEx. Note that this does not solve strat's problem with this RegEx, as he is looking for a substitution and not a matching, and as it is nested it will be really hard to do a substitution with it. This can be understood as a challenge ;-).
Still, I modified the RegEx a bit to work with strat's problem, at least for matching 
use re 'eval';

$begin = '[xyz]'; $end = '[/xyz]';
$string = '[xyz]level 1.1 [xyz]level 2.1[/xyz] rest of 1.1 [/xyz]';
$re = qr{
    \Q$begin\E
        (?:
            (?> (?:(?!=\Q$begin\E|\Q$end\E).)+ )
            |
            (??{ $re })
        )*
    \Q$end\E
}x;

print 'Yeah!' if $string =~ $re;

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Cheers, CombatSquirrel.
Entropy is the tendency of everything going to hell.

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Re^3: "Not containing something" in substitution
by Aristotle (Chancellor) on Aug 28, 2003 at 12:57 UTC
    Why? 
    use strict;
use warnings;
use re 'eval';

my $begin = qr!\Q[xyz]!;
my $end   = qr!\Q[/xyz]!;

my @match;

my $re;
$re = qr{
    $begin
    (
        (?:
            (?> (?:(?!=$begin|$end).)+ )
            |
            (??{ $re })
        )*
    )
    $end
}x;

$_ = '[xyz][xyz]level 1.1 [xyz]level 2.1[/xyz] rest of 1.1 [/xyz]';

1 while s!$re!<xyz>$1</xyz>!;

print;

__END__
<xyz><xyz>level 1.1 [xyz]level 2.1</xyz> rest of 1.1 </xyz>

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    Makeshifts last the longest.

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[d/l]

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