I've read suggestions mentioned above, and it's all rigt, but following the philosophy of Perl - you can do one thing in more than one way :-)
You can try to set all the parts in 1 file... Fork them and gather the results... There are also some wired solutions (unsorted):

1. sockets
2. files with flock()
3. pipes

If you use sockets, then you write a server for them and the children are the clients that just send the results.
Files with flock() are also some solution - in this case you have to read only from one handle.
Pipes - almost the same as the sockets, only the loop differs and the data model is slightly different. When using sockets and pipes you would probably use some loop to skimm through open handles and check if there is something to read.

If this script is to be simple as far as possible, i would use files with flock() i think.

Greetz, Tom.