#!/usr/bin/perl -l

use strict;
use warnings;

my @blacklist = ('evil', 'bad', 'wrong');
#$a and $b are bad variable names due to sorting things
my $aa = "this string contains no blacklisted tokens";
my $bb = "this string is evil and wrong";

# The regex should express the blacklist is such a way that
# # it will match on any string which DOES NOT contain any of
# # the tokens in the blacklist, and it will fail to match on
# # any string which DOES contain tokens from the blacklist.
#
my $regex = qr/^(?!.*(?:evil|bad|wrong))/;

if (($aa =~ m/$regex/) && !($bb =~ m/$regex/)) {
   print "Woohoo";
}