straight from the Hugo source

So I asked Kent Tessman about exactly what was going wrong when something like my ClearArray routine uses up all of the UNDO memory. He answered:

The way Hugo's undo currently works, it stores a stack of individual commands, and basically sticks a bookmark in where a player command would be. Sorry, but the first 'individual commands' I mean 'program statements' or 'program commands'. So when you assign a variable or -- as you discovered, a single array element -- it uses an undo slot. Now, there are lots of them, but the default (and essentially at this point standard) engine has an arbitrary limit to keep memory usage down.

So that'll be an interesting thing to keep in mind in the future. I then asked him if, memory-wise, array elements, variables, and property elements- and the setting of- are interchangeable. He answered:

For the most part.  I mean, basically what Hugo does is allocate a big chunk of bytes, and divvies it up.

 So I think the lesson to be learned from that is to not put all of your state-tracking changes in one basket but to split them up between arrays, property arrays, and variables. Whatever the case, most importantly, don't write code that sets many of these values needlessly.

Anyhow, I'll try to have a new version of Roodylib up soon.