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What's the best way to fetch data from multiple sources asynchronously?
One word: POE. POE is an excessively cool asynchronous framework that makes these sorts of things a breeze. The idea is that every thing you do with POE will be non-blocking, for example, querying a web page, talking to a db, and so forth, so you can launch as many of these as you want, without the hassles of dealing with IPC or threads. Check out some of the examples in the cookbook for sample applications that demonstrate the principle. Then see CPAN's massive collection of POE::Components.