I think you could distribute a script to all the remotes that ftp'ed the file back to the central server. Of course, you might be able to schedule a simple batch script to do that-- as opposed to having to put perl on all those machines.

Or assuming you have mounted the central server as a drive on all the remotes, instead of FTPing the file you just copy it over. Making sure to perhaps change the filename so there aren't collisions, or giving each remote its own subdir on your server.