IP逆引き

use Net::DNS::Resolver;
use Socket;

sub ip2host {
    my $q = Net::DNS::Resolver->new->search(shift, 'PTR') or return;
    foreach ($q->answer) {
        next if $_->type ne 'PTR';
        return $_->rdatastr;
    }
}
print ip2host(shift), "\n";

蝶やっつけ。蝶てきとう。