`Symbol’s function definition is void: \(setf\ match-string\)`while using `push`

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The first argument for `push` is the element, the second argument is the place you want to put it. I think you have the order wrong, and it should be (push (match-string 0) commands)

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Also worth noting: OP has written self-modifying code, by let-binding empty lists which will get mutated. And that `(if (not` should be an `(unless`.