sub new-nsqry{
  my ($res, $IP) = @_;  # Note: $res is created OUTSIDE the sub ...
 
  my $query = $res->query($IP, "PTR");
  
  if ($query) {
      foreach $rr (grep { $_->type eq 'PTR' } $query->answer) {
          print $rr->ptrdname, " : $IP\n";
          return $rr->ptrdname;
      }
      return undef;
  }
  else {
      warn "query failed for $IP: ", $res->errorstring, "\n";
      return undef;
  }
}