I think you can create an account on DynDns or No-Ip (the basic service is free), and install the client on a Windows or Linux machine of your LAN. This client will let DynDns/No-Ip know your address every now and then (you choose how frequently). Then, from the outisde, you just need to dig something like nathanvit.no-ip.org to know the IP address of your router.

The solution isn't Perl based, but it's easy and should work smoothly.

Michele.