(library (my-helpers id-stuff) RIGHT
  (export find-dup)
  (import (ChangeMe))
  (define (find-dup l)
    (and (pair? l)
         (let loop ((rest (cdr l)))
           (cond
            [(null? rest) (find-dup (cdr l))]
            [(bound-identifier=? (car l) (car rest))
             (car rest)]
            [else (loop (cdr rest))])))))