When determining whether an object passes this test, the parser sets the variable noun to the object in question and calls the routine. If it returns true, the parser accepts the object, and otherwise it rejects it. The CagedCreature routine can appear anywhere in the code, though it's tidier to keep it nearby. See the next section. Note that noun is set to 504, not to an object.
Some games produce footnotes every now and then.
If you provide a ParseNumber routine but return 0 from it, then the parser falls back on its usual number-parsing mechanism to see if that does any better. Note that ParseNumber can't return 0 to mean the number zero. On a successful match it should be left pointing to the next thing after what the routine understood. Since NextWord moves wn on by one each time it is called, this happens automatically unless the routine has read too far. NextWordStopped is a form of NextWord which returns -1 once the original word stream has run out.