Thanks Matt! There were a bunch of other problems after that, but I managed to solve them all, and by all appearances I've successfully updated the extension for build 6G60. Interested parties can find it
here. I'm going to play around with it, and if it works just fine then I'll submit the update to the inform7 website.
EDIT: more specifically, I've defined the number variables that were previously only defined in 'let x be y' statements, got rid of the redundancies in statements like 'increment x by one', and changed 'not a verb I recognise' to 'the not a verb I recognise error'.