Generally speaking, I would print out the return values as I received them, but then, at the end, print out a nice pretty, ordered list. This allows for systems that respond quickly to show up quickly, and systems with lag responding to not delay the quick ones, at least during the running.

Where to get started - that is a matter of preference. I had someone here recommend AnyEvent and Coro to me ages ago, and that's what I'm using for the CB stats and last hour of cb updates (it's all in a single process and a single thread, making http calls to Perlmonks, both for downloading and uploading, and updating databases, and actually having a built-in chatterbox client as well). There's a pretty good chance that Coro won't be available in an RPM on RHEL/CentOS. However, Yes, even you can use CPAN might still be worth a read for your situation.