#!/usr/bin/perl -T
use strict;
use warnings;

# $Id; $

use Net::DNS;

my $res = Net::DNS::Resolver->new();
$res->recurse(1);
$res->retry(1);
$res->persistent_udp(1);

while ( defined(my $line=<>) ) {
    chomp $line;
    ptr_query($line);
}

sub ptr_query {
    my $addr  = shift;
    my $query = $res->send( $addr, 'PTR', 'IN' );
    my $found = 0;

    if ( !$query || $query->header->ancount == 0 ) {
        print "$addr|n/a\n";
        return;
    }

    my @answer = $query->answer;
    for my $rr (@answer) {
        next if $rr->type ne 'PTR';
        $found++;
        print "$addr|" . $rr->rdatastr . "\n";
    }

    if (!$answer_found) {
        print "$addr|n/a\n";
    }

    return;
}