Any Perl CGI script should be able to use this module, without any specific FastCGI coding or adjustments.
I can tell you right away that it won't work perfectly. What you're doing is mostly the same as what Apache::Registry does. If someone defines a global, it will still be there the next time the script is run. If they load a module, it will still be there, and it will not reload even if they change the module. There's a lot of mod_perl documentation discussing these issues and how to cope with them.