I applaud (and upvoted) your post, but would just point out one thing. Since you are retrieving the entire contents of the urls as a single string, and then processing that string using a single regex, the cost of pushing the data to a shared queue, reading it back to process it and then passing the concatenate results to another thread via another queue is going to cost far more than it will ever save.

You are also starting multiple threads all appending to a single file, but you are not mutexing the writes. In the olden days, it was generally considered safe to write append mode to files from multiple processes because CRTs guarenteed 'atomic' writes in append mode. It's not at all clear if any or all builds Perl uses the underlying CRT for this. Nor is it clear whether any or all CRTs make the same guarentees when called from multipe threads.