Have you looked at perlipc? It has some very useful examples of using pipe and fork to do bi-directional communication between a process and "itself." Another option would be to use socketpair (this is also described in perlipc).

Yet another option would be to write a client/server app using sockets; you can set up a server that has the list of files to search, then set up some clients that communicate via sockets with the server. The server sends a filename to a client, and the client searches it, then sends back the results over the socket.

You wouldn't need to use temporary files in any of these implementations.

Just some ideas. Definitely take a look at perlipc.