a solution for SRFI-72's "Improved hygiene" using syntactic closures

gistfile1.scm

;; A solution for SRFI-72's "improved hygiene" using syntactic closures.
;; See also http://srfi.schemers.org/srfi-72/srfi-72.html#hygiene

(let-syntax ([main (sc-macro-transformer
                     (lambda (form env)
                       (define (make-swap x y)
                         `(let ([t ,x])
                            (set! ,x ,y)
                            (set! ,y t)))
                       `(let ([s 1] [t 2])
                          ,(capture-syntactic-environment
                             (lambda (env)
                               (make-swap (make-syntactic-closure env '() 's)
                                          (make-syntactic-closure env '() 't))))
                          (list s t))))])
  (main)) ;=> (2 1)