Well, it has been discussed that Net::Ping is due for a bit of maintainance, or possibly a more thorough overhaul, because of the fact that it doesn't report ICMP packets correctly unless it is run as root, which presents a security problem.
in reply to Data Structures wanted; apply within.
It is an important (not to mention popular) module, so not only would it be a good candidate for your project, but also an opportunity to learn about network and socket programming, and you also might benefit from a bit of parallel programming while you're at it.
Another aspect is that you'd get the chance to optimize the algorithms that the module uses, since there are several different approaches that would likely work in the actual implementation.
In any case, good luck in your project, whatever you choose!