test2.scm

(define-syntax l
  (syntax-rules ()
    ((_ P Q ...) (lambda (P) Q ...))))

(define c 1)

(define-syntax macro
  (syntax-rules ()
    ((_ P) ((l c (list c P)) c))))

(let1 c 2 (macro c)) ; => '(1 2)

; This macro expansion is wrong.
; -> ((l c (list c c)) c) => '(2 2)

; To avoid this expansion, we should expand this form as below.
; -> ((l c0 (list c0 c)) 1)
; -> ((lambda (c0) (list c0 c)) 1) => '(1 2)