(let ((a 10) (b 11) (c 12) (d 13))
  (letrec ((g (lambda ()
                (+ a b c d)))
          )
    (list
      (g) 

      (fluid-let ((a 1) (b 2) (c 3) (d 4))   ; in this fluid-let a is temporarily assigned 
         (g))                                ; to 1, b to 2, c to 3, and d to 4.

      (g)
    )
  )
)

; (46 10 46)