Dominique has already given one good answer to this, but as is always the way with something as complex as pattern-match, there is more than one way to do it.
Another possibility, which is sometimes a useful trick to know, is to use more than one answer pattern. That way you can first get rid of things you want to mark wrong, and then you don't have to worry about that any more when you are making the rule to grade what is right.
Answer 1: match_w(not) -> 0%, and perhaps give some feedback telling them not to use the word 'not'.
Answer 2: match_mow(native New Zealand) -> 100%
Another possibility, which is sometimes a useful trick to know, is to use more than one answer pattern. That way you can first get rid of things you want to mark wrong, and then you don't have to worry about that any more when you are making the rule to grade what is right.
Answer 1: match_w(not) -> 0%, and perhaps give some feedback telling them not to use the word 'not'.
Answer 2: match_mow(native New Zealand) -> 100%