If you're finding that you have a "doesn't scale well" problem (ie, your hash or array are simply getting too large, and possibly could even get larger), one option is to move to a database solution. You're already pondering that option when you talk about 'tie hash'; that's probably going to lead you to a hash tied to a database. But you may just find that rethinking your needs and designing a solution around a database while forgetting about the hash altogether will give you a better approach.

Of course this is speculation; we don't know what you're really trying to do, and thus can only take a blind stab at how to help. But a lightweight database such as SQLite can really help when you find that it's just not practical to slurp a big hash into memory.