S9 LIB  (and-let* <binding> ... <body>)  ==>  object

        (load-from-library "and-letstar.scm")

Each <binding> has the form (<variable> <expression>) and binds
the given <variable> to the normal form of <expression>.

Like LET* AND-LET* evaluates its <bindings>s in sequence, so each
<expression> is evaluated in an environment that includes all previous
<binding>s of the same AND-LET*. Unlike LET*, though, AND-LET* returns
#F immediately as soon as one of its <expression>s evaluates to #F.
Only when all <expression>s evaluate to non-#F values, it evaluates
<body> and returns its value.

This is only a subset of SRFI-2 AND-LET*.

(and-let* ((a '((x . 1)))
           (a (assq 'x a)))
  (cdr a))                   ==>  1

(and-let* ((a '((x . 1)))
           (a (assq 'z a)))
  (cdr a))                   ==>  #f
