Now this part surpises me:
Shared data in perl's ithreads is very expensive, both in terms of speed and memory usage. A shared scalar variable usually has a copy in every thread that uses it, plus a separate shared copy. When you assign to a scalar, the thread's copy is updated, then that data is also copied to the hidden shared copy. When you read from a shared scalar, the data from the hidden shared copy is copied to the thread's one. Thus if you have N threads all accessing a long string variable, your memory usage will tend towards (N+1) times the length of the string.
I would have thought Perl use references for everything, not complete copies, making things much less memory and resource intensive...
Try to avoid having complex, deeply-nested shared data structures
Doh! One of the ideas was to use an XML::Simple object to store server data and each thread would update that object based on possible changes ... looks like I might have to keep with fork() with a slight restructure in how i would modify that main hash.
We put the 'K' in kwality!