That data won't be shared after forking is to be expected; forking creates a whole new process that is completely seperate from the old one (on UNIX-like platforms, this is simulated on Windows, see perldoc perlfork.)

If you want to share data between the processes, you can look to the IPC::Shareable or IPC::ShareLite modules though I don't know think they'd work on windows. You could also try a "real" database, or some DBM file that you would lock for every read and write.

Note that $::PRESISTENT_HASH is not the hash created with my %PRESISTENT_HASH. The my statement creates a lexically scoped (to the file the my is in, in this case) variable, not a global variable, which is what %::PRESISTENT_HASH is.