If it is standalone, then my scripts will need some hokey magic with message queues or some such interface.

Why would it need that? Can you explain a little more about what this UDP server is supposed to be doing? I can't understand why you think it would be simpler to have a CGI script become a server.

That is actually the current interface - a standalone server written in C waiting to accept udp messages, and when one is accepted, just do a system call with the contents of the message to launch a new browser with an argument of a new cgi script.

There's no reason to use a system call to make an HTTP request. Just use something like LWP if that's what you need to do.