my %results;
@goodstuff = (1,2,3,4,5);
@badstuff = (1,3);

for (@goodstuff) { $results{$_}++ }
for (@badstuff}  { $results{$_}++ }

for (keys %results) {
  if ($results{$_} == 1) {
    print "Value: " . $_ . " was found in only one array\n";
  }
}