If you are using mod_perl, you could set the hashes in (a module use'd in) the startup.pl script, thereby sharing it with all apache childs. If you change the hashes afterwards, they won't be shared anymore - assuming Unix copy-on-write mechanisms apply; i.e. you're using a forked apache - I don't know what the deal is with data sharing on apache 2 with threads.

Otherwise, you might want to take a look at Cache::Cache or IPC::ShareLite.

Update: I just remembered DBM::Deep, which might be easier to merge into your existing code. Never really tested it, though the documentation looks very promising.

Hope this helps,
Joost.