How's about

use strict;

my @sites = (
    "http://www.rtfm.com", "http://www.alottatax.com",
    "http://www.kingdom.com/cgi-bin/script.pl"
);

my $blacklist = join '|', map quotemeta, qw/ cgi blabla testme /;

for(@sites) {
  printf "%s %s\n", $_,
                    $_ =~ /($blacklist)/ ? "blacklisted - $1" : 'ok';
}

__output__

http://www.rtfm.com ok
http://www.alottatax.com ok
http://www.kingdom.com/cgi-bin/script.pl blacklisted - cgi
[download]

See. perlre and quotemeta for more info. Also a module that might be of interest - Regex::Presuf.
HTH

_________
broquaint