for ($candidate = 12345;
     $candidate <= 98765;
     $candidate++) {
       if (check_prime($candidate) &&
           check_digit_3($candidate) &&
           check_digit_2($candidate) &&
           check_digit_5($candidate) &&
           #check_duplicates($candidate) && # problem?
           check_digit_1($candidate)) {
         print "$candidate\n";
       }
}