#!/usr/SD/perl/bin/perl
use Socket;

while (<>) {
    s/(\d+\.\d+\.\d+\.\d+)/resolve($1)/e;
    print;   
}   

sub resolve {
    my ($ip) = @_;
    
    my $iaddr = inet_aton($ip);
    return $ip unless $iaddr;
    
    my $name = gethostbyaddr($iaddr, AF_INET);
    return $name if $name =~ /\S/;
    return $ip;
}