用Perl进行DNS反向查询

#!perl
    use Net::DNS;

my $res = Net::DNS::Resolver->new;
    my $query = $res->search("4.2.2.4");

if ($query) {
        foreach my $rr ($query->answer) {
        next unless $rr->type eq "PTR";
        print $rr->ptrdname, "/n";
        }
    } else {
        warn "query failed:", $res->errorstring, "/n";
    }