anchor.diff:  
   
    (multiple-value-bind (ns pfx)
  -     (ensure-prefix *foo* *foo.ex* *r*)
  +     (bind-prefix *foo* *foo.ex* *r*)
      (values (eq pfx *foo*) ns )
      )
     ;; => T, #<structure-object ...>
  
positive.code:  ;;    => 2
  
   (handler-case
       (ensure-prefix (string (gensym "NS-")) "http://bar.example.com/" *r*)
     (namespace-prefix-bind (c)
       (warn "Caught bind signal: ~s" c)
       (continue c)))
  
negative.code: ;; (aref (namespace-registry-namespace-table *r*) 0)
  
  
   (bind-prefix "bar" *foo.ex* *r*)
   ;; ^ call multiple times, should not be duplicating prefixes
  
   (handler-case
       (bind-prefix "bar" "http://bar.example.com/" *r*)
     (namespace-prefix-unbind (c)
       (warn "Caught unbind signal: ~s" c)
       (continue c)))
  