sub next_prime_iterator {
   my $num = shift(@_);
   return 3   if  $num < 3;
   do { $num += 2 } until is_prime($num);
   return $num;
}

sub is_prime {
   my $guess = shift(@_);

   my $divisor = 3;
   my $quotient;
   while(1) {
       $quotient= $guess / $divisor;
       return 1   if  $quotient < $divisor;
       return 0   if  int($quotient) == $quotient;
       $divisor += 2;
   }
}