Reverse DNS lookup in perl

use Net::DNS;
my $res = Net::DNS::Resolver->new;

# create the reverse lookup DNS name (note that the octets in the IP address need to be reversed).
my $IP = "209.85.173.103";
my $target_IP = join('.', reverse split(/./, $IP)).".in-addr.arpa";

my $query = $res->query("$target_IP", "PTR");

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

use Socket;
$iaddr = inet_aton("127.0.0.1"); # or whatever address
$name  = gethostbyaddr($iaddr, AF_INET);

perl -MSocket -E 'say scalar gethostbyaddr(inet_aton("79.81.152.79"), AF_INET)'

$ip = "XXX.XXX.XXX.XXX" # IPV4 address.
my @numbers = split (/./, $ip);
if (scalar(@numbers) != 4)
{
    print "$ip is not a valid IP address.n";
    next;
}
my $ip_addr = pack("C4", @numbers);
# First element of the array returned by gethostbyaddr is host name.
my ($name) = (gethostbyaddr($ip_addr, 2))[0];