I'd say the biggest boost came from modules, and the control of side effects (by, among other things, limiting the use of global variables). Now, do you see a

I'd say the biggest boost came from modules, and the control of side effects (by, among other things, limiting the use of global variables). Now, do you see a significant additional boost that were provided by the various OO styles out there? More specifically, what significant advantage do classes have over modules?