Question

I may simply misunderstand the difference between the two: If the only difference between a subroutine and a function is that a function has the option of returning a value while a subroutine does not, then in what situation would you use a subroutine? Why wouldn’t you always use a function?

Answer 1

I use Subs when I need a ‘named piece of code’ that does not return any information, but is called only for its side effects. I use Functions when I need a ‘named piece of code’ that returns some information (and (normally) does not have side effects). I’m glad that I can state my intentions in VBScript explicitly.

Added: Why @AutomatedChaos’ proposal (comment) is misguided:

1. You shouldn’t write code before your design is settled. Either you don’t need to check the result of a file delete action (then write a Sub) or you have to (then write a Function). You may later realize that you have made a mistake, but then you’ll have to change more than just the npc’s type.
2. Checking an action’s result in a Function is a promise that your script will always handle a failure of the action reasonably (because each call of the Function is obliged to check the return value). To freely give the license to call such a Function as a Sub invalidates this promise.