Some easy ones (?)

[Alan Bawden <ALAN@AI.AI.MIT.EDU>]

    Date: 26 Jul 86 18:22:55 PDT
    From: masinter.PA at Xerox
    if you want simplicity, allowing duplicate names and just saying that
    the last one shadows all the rest, ...

    (defun foo () (let((a 1)(a 2))
    	a))

    would return 2, etc....

I was going to suggest exactly this.  The only thing I would add is that in
cases like the above, a good compiler should issue a warning about the
variable named "A" that was bound but never referenced.  Thus most (not
all) cases where a duplicated variable was the result of programmer error
will be brought to the programmer's attention.  Other cases, such as the
LET* examples recently exhibited, will not provoke this warning from the
compiler.