in reply to Speed of Perl Regex Engine

Does it need to be a regex? If you can live with an exact match, then I'd use a hash:
my %want_global = map { ($_ => 1) } qw( THIS THAT ANOTHER ); ... if ( $want_global{$global} ) { ... }
If you really need to have regexes, then put them in an array instead of a single regex, it will generally perform better than a joined single regex (and put the most likely things to match first, if possible):
my @wanted_re = ( qr/^AB/, qr/^CD/, ); sub want_global { my $g = shift; for my $re (@wanted_re) { return 1 if $g =~ /$re/; } return; }
Update: I see that maybe you want 'unwanted global' logic...whatever...the above still applies...adjust to suit needs.