#!/usr/bin/perl -w
use strict;
use Socket;

while (<DATA>) {
    if (/^Listen/) {
        chomp;
        my ($ip) = $_ =~ m/^Listen\s([\d\.]+):?/;
        my $host = gethostname($ip) || "unknown";
        print "IP:$ip HOST:$host\n";
    }
}

sub gethostname {
    my $ip = shift;
    my $iaddr = inet_aton($ip);
    return gethostbyaddr($iaddr, AF_INET);
}

__DATA__
Listen 1.2.3.4
Listen 5.6.7.8:9735
rubbish
Listen 209.131.36.158
Listen 11.12.1.4:8080
more rubbish

##</code><code>##

IP:1.2.3.4 HOST:unknown
IP:5.6.7.8 HOST:unknown
IP:209.131.36.158 HOST:f1.www.vip.sp1.yahoo.com
IP:11.12.1.4 HOST:unknown