sub alpha_num_cmp {
   my($a, $b) = @_;
   if (( $a =~ m/\D/) || ($b =~ m/\D/) ) 
      {                      #look for a non-digit
        return ($a cmp $b);  #string compare
      }
   return ($a <=> $b); #straight numeric comparison
}
#used like: sort alpha_num_cmp @array;