use lib "./lib"

Relative paths are fragile, use a full path :) it can be dynamic ( see File::FindLib, FindBin, use lib $lib_dir not working )

But it uses a database behind the calcs, and I think I must avoid that.

The FAQ says to use database to store results, so you don't need it, but if you need one, you can always use DBD::SQLite

Am I on the right track in that thinking? I'm worried about building a large data structure in memory on a server I don't own. I'm wondering if a module already exists that may do some of this already?

I feet not :)

A casual look at Math::Business::HMA/ Math::Business::StockMonkey::FAQ ... shoes hints it doesn't use a lot of memory (it doesn't build a giant array), so I'd just use stockmonkey, but I would do local testing to check for memory growth ( Devel::NYTProf, Devel::Leak Devel::LeakTrace, WeakRef )

*hint* the memory question would make a good addition to Math::Business::StockMonkey::FAQ

I feel my shoes with my feet , wanna take good care , remain elite