In the system messages, there's also (from memory) things like ${entity}, ${verb}, ${noun} and so on. Are these documented anywhere?
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Again from memory, I think there's ${noun2}. These can be pretty useful in the right circumstances. For example, I've noticed that when I GET ALL and one of the items is scenery, it says something like "You can't get that." followed by "You get the apple." I'd prefer it to say, "You can't get the tree." followed by "You get the apple." I think I might change the system message to say "You can't get ${entity}."