Hi,
yes, 'not' works better:

#!/usr/bin/perl
use strict;
my $regex = 'foo';
my $test_string= 'bar';

print 'no match 1',"\n" if not $test_string =~ /$regex/;
print 'no match 2 ',"\n" if ! $test_string =~ /$regex/;
print 'no match 3', "\n" unless $test_string =~ /$regex/;
[download]

returns:

no match 1
no match 3
[download]

Regards,
svenXY