Wrong function. The one you're using is to look up the IP by name.

print join ".", unpack 'C*', scalar gethostbyname('mediamind.be');
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-->

66.33.0.165

The fucntion you need to use, is gethostbyaddr(). Socket is used for the constant AF_INET, though you could use it for the more robust function inet_aton(), too, instead of the pack+split. See the example in perlfunc:gethostbyaddr.

use strict;
my $ip = join ".", unpack 'C*', scalar gethostbyname('mediamind.be');
print "IP = $ip\n";

use Socket;
my @result = gethostbyaddr pack('C*', split /\./, $ip), AF_INET;
use Data::Dumper;
$Data::Dumper::Useqq = 1;
print Dumper @result;
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-->

IP = 66.33.0.165
$VAR1 = "mediamind.be";
$VAR2 = "";
$VAR3 = 2;
$VAR4 = 4;
$VAR5 = "B!\0\245";