$re[0] = qr (.*(?!system))i;
$re[1] = qr (system)i;
$v[0] = "oneitem";
$v[1] = "anothersystem";

for $a (@v) {
  for $r (@re) {
    print "\nRegex: $r\tValue: $a\n";
    if ($a =~ /$r/) {
      print "$a matches $r\n" ;
    }
  }
}

##</code><code>##

Regex: (?-xism:.*(?!system))    Value: oneitem
oneitem matches (?-xism:.*(?!system))

Regex: (?-xism:system)  Value: oneitem

Regex: (?-xism:.*(?!system))    Value: anothersystem
anothersystem matches (?-xism:.*(?!system))

Regex: (?-xism:system)  Value: anothersystem
anothersystem matches (?-xism:system)