The threads themselves seem to work fine until mod_perl is switched on. The application is live in it's non mod_perl version at the moment. But yes, it took us a long time to get to the stage where we got something other than bizarre errors in the log. And with mod_perl, they just get ever stranger.

We actually started as non-threading, using a simple Perl powered web server (HTTP::Server based I think it was) plus LWP::Paralllel on the front-end to connect to it with different parameters, which it then went off and processed. But it all became too slow and unwieldy as the number of searches increased and the Perl webserver forked more and more. Returning to an LWP::Parallel process connecting to a more stable backend (like a light web server) is tempting, if only for scalability reasons.

But darnit, when you've come this far, sometimes you just want things to work. :)