R4RS 4.2.2  (let* <bindings> <body>)  ==>  object

Syntax: <Bindings> should have the form

((<variable> <init>) ...),

and <body> should be a sequence of one or more expressions.

Semantics: LET* is similar to LET, but the bindings are performed
sequentially from left to right, and the region of a binding indicated
by `(<variable> <init>)' is that part of the LET* expression to the
right of the binding. Thus the second binding is done in an environment
in which the first binding is visible, and so on.

(let ((x 2) (y 3))
  (let* ((x 7)
         (z (+ x y)))
    (* z x)))          ==>  70
