Depending on your network's topology and complexity, you might find it most reliable to query your router. I have a fairly inexpensive Netgear router that has various configuration web pages, one of which offers a list of assigned IP's and their names. Just screen scrape the router's attached-devices page, and process the results accordingly.

To do it this way, assuming your router serves a web configuration page, just look at using WWW::Mechanize, or LWP::UserAgent (from which WWW::Mechanize inherits.