(define cwd (make-parameter "/home"))

(define (foo x)
	(displayln (cwd))
	(displayln x))
	
(define-syntax-rule (bar d body)
	(parameterize [(cwd (string-append (cwd) "/" d))]
		(begin body)))
	
	
(foo 12)
(bar "myuser"
	(begin
   (foo 12)
	  (bar "another_dir"
		  (foo 14))))