Okay, let me give a simpler example: (defun first-two (list) (assert (>= (length list) 2)) (list (first list) (second list)

Okay, let me give a simpler example: (defun first-two (list) (assert (>= (length list) 2)) (list (first list) (second list))) In a language which doesn't normalise the case of symbols you could in theory work around that by capitalising or upper-casing either the function or the variable, but that's still not a particularly elegant solution.