Just talked to a customer. It seems like the solution to their problem would be a system where every client has its own web server and database which is synced with a central database when the client is online. The system should run on 30000 Linux (!) laptops and and a few legacy windows machines.
I think a pure Perl solution with a Perl web server, a Perl database and a Perl application packaged as a par would work here (Raw speed is no issue). It certainly is an interesting project.