Why does my Macro get expanded 8 times?

["Daniel L. Weinreb" <DLW@alderaan.scrc.symbolics.com>]

    Date: Wed, 6 Jul 88 12:26 CDT
    From: Gumby@MCC.COM (David Vinayak Wallace)

    How does this manage to do the right thing?  According to CLtL p 60 you
    can have any number of declarations and documentation strings (although
    it's not clear what multiple doc strings imply) before the body of the
    expression.

When the compiler sees the NIL, it is obvious that the NIL is not a
declaration, and is not a documentation string.  Therefore, it knows
that there are no more declarations and no more documentation strings.