while(<STDIN>) {
  chomp;
  if (/^Received:[^\[]+\[(\d+)\.(\d+)\.(\d+)\.(\d+)\]/) {
    $n=`host $4.$3.$2.$1.$ARGV[0] 2>&1`;
    exit(0) if ($n=~/$ARGV[1]/m);
  }
}
exit(1);