The same code(now working) is being used to accomplish that, actually. I use the same regexp when the user supplies the expression to verify its validity, without doing any evaluation on it:

while ($tmp =~ /\(((?:[^()])*?)\)/) {
        my $assert = $1;
        $assert =~ s/\|/\\\|/g;
        $tmp =~ s/\($assert\)/$1/;
}
($tmp =~ /\(|\)/) ? print "Don't match.\n" : print "Match.\n";
[download]

Just as a purely hypothetical example. Though, I will definitely look into those modules, as I'd not heard of them before. Thank you for the link.

~Moe~