SRFI-83 states:

  "No identifier can be imported multiple times, defined multiple
  times, or both defined and imported."

I find useful several modules which extend R5RS or other module's
procedures.  For instance, SLIB's commutative-ring "allows one to use
basic Scheme numeric functions with symbols and non-numeric elements
of commutative rings."

     (require 'commutative-ring)
     (define a 'a)
     (define b 'b)
     (+ (+ a b) (- a b))  ==>  (* a 2)

Does SRFI-83 allow redefinition and export of R5RS procedures?

Does SRFI-83 allow some way for a module to import, wrap, then export
an identifier?