is there a better mechinism for interprocess communication than simply using a file?

On UNIX, you might want to allocate a shared memory segment and have the forked calculating process write it's results to it. See perlipc. The CGI spawning the process sets up the segment and passes it's shmid to the web client, so on subsequent calls a new CGI process knows which segment to read. If the size of the data isn't constant (e.g. growing), a database might be a better approach.

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}