(defun variable-p (x) (and (symbolp x) (char= (char (symbol-name x) 0) #\?)))文字列の要素をとり出すには,charの他にeltでも大丈夫です.
<cl> (symbol-name 'abc) "ABC" <cl> (symbol-name '?abc) "?ABC" <cl> (elt "abc" 0) #\a <cl> (char "abc" 1) #\b <cl> (variable-p '?a) T <cl> (variable-p '??) T <cl> (variable-p '*?) NIL <cl> (variable-p 'abc) NIL