Note that POE isn't about "threads", basically your program is a single process, and the tasks are split into atomic tasks called events which should be non-blocking.

For multiple events to coexists your POE program should use POE Wheels or Components that are not blocking (usually select based).

To run blocking pieces of code that aren't POE aware, such as WWW::Mechanize, you may spawn a POE::Wheel::Run session which is in fact another process so that the rest of you application doesn't block.

However, this wouldn't justify the use of POE because you'd either spawn a new process for each request, or use a pool of processes for each WWW::Mechanize client, each process fetching and parsing a page one at a time.

POE::Component::Client::HTTP isn't so powerfull as WWW::Mechanize, but you might use it to fetch the page contents, and then another session (separate process or not) do the processing of the page's content.

POE Cookbook - Web Client shows a simple usage of POE::Component::Client::HTTP