Here's a few stupid questions:

1. Why are you using threads instead of processes? Apache's children are processes and it's extremely robust. Apache doesn't necessarily have to serve HTML, either. It's a CGI server which can serve anything you want. And, Perl can be tightly intergrated into it.
2. Why not set up the shared datastructure as a SOAP process and have your children communicate with it? That way, you can even have your objects on another server and still be ok.

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We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.