Net::MAC::Vendor provides a way to get information about the vendor from the MAC (Media Access Control) number which is associated with Ethernet hardware. It's handy for jobs like working from a router's arp table to what the hardware actually is (e.g. Nintendos or something for which it's hard to find what the IP address is).
The "lookup" part of the module works correctly although not quite as described (reported as rt.cpan.org bug #44963) - the vendor is the first part of the array and the address part is the rest. However, why does the module even bother returning the postal address? Unless we are planning some kind of mass mail shot to ethernet hardware vendors, the only information anyone is really likely to want is the vendor. Why not just provide that, and people who actually need the postal address for some reason could go to the IEEE web site.
Also, the dependence on the DBM::Deep module for caching seems unnecessary to me. The information which needs to be stored and read is an extremely simple fixed format which could be read into a hash and appended to a text file without the need for any dependencies, particularly one as complex as this.