#/usr/bin/perl

require 'sys/socket.ph';

while(<>){
   if(/\b([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+)\b/){
     $addr = pack('C4', split(/\./, $1));
     ($name, $rest) = gethostbyaddr($addr, &AF_INET);
     if($name) {s/$1/$name/;}
   }
   print;
}