Right on, assuming that you're looking at the MAC address(es) of your local machine. If you want to find the address of a remote machine, it might be in your local ARP cache. Try parsing the output of /usr/sbin/arp on a Unix machine (keep in mind that the arguments to arp vary by operating system).

Also, if the MAC address of interest isn't in your ARP cache, you can try pinging it with Net::Arping. It will allow you to ping a host using ARP packets and get the MAC address directly from the reply. This is a cool module, even if the documentation leaves a bit to be desired.

Your system's ARP cache should cache the MAC addresses of machines on the local network with which it has recently communicated, so you may not even need to install the module depending on your environment.

Here's another link on ARP and Linux if you're interested.