You don't need an external module to just lookup hostnames into IP addresses.

If your hosts only resolve to a single address, you can use the following:

#!/usr/bin/perl -w

use Socket;

my $hostname = "www.perlmonks.com";

my $ipAddress = inet_ntoa(inet_aton($hostname));

print "IP address of $hostname is $ipAddress.\n";
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Update: Just to clarify, by "external" module I mean one that's not included in the ActiveState distribution of Perl.