(define (remove-comment str)
  (regexp-replace-all #/\/\*(.+?)(\*\/|$)/ str ""))

(print (remove-comment "AAA"))                  ; => "AAA"
(print (remove-comment "AAA/*BBB*/"))           ; => "AAA"
(print (remove-comment "AAA/*BBB"))             ; => "AAA"
(print (remove-comment "AAA/*BBB*/CCC"))        ; => "AAACCC"
(print (remove-comment "AAA/*BBB/*CCC*/DDD*/EEE")) ; => "AAADDD*/EEE"
(print (remove-comment "AAA/a//*BB*B**/CCC"))      ; => "AAA/a/CCC"