I don't understand the part about forgetting to call zip_init. But I tend to agree with tilly about using a separate function.

It seems that memoize's cache over tied hash would work, or maybe you'd like to periodically dump your db into Tie-MmapArray files, which seems to resemble your request of an auto init function. You'd pick which pre-prepared file to tie in after getting user input, and voila your memory is useable.