anchor.diff:  
   This is similar, but not identical, to SEARCH.
   
  -     (search nil \"foo\") => T
  -     (search \"nil\" \"nil\") => NIL
  +     (search nil \"foo\") => 0
  +     (search \"nil\" \"nil\") => 0
        (string*= nil \"foo\") => NIL
        (string*= nil \"nil\") => T"
       (call search s1 s2))
  
positive.code:   (defcmp (string~= string-tokenp) (s1 s2)
      "Does S1 occur in S2 as a token?
  
  This is equivalent to
       (find S1 (tokens S2) :test #'string=),
  but without consing."
      ;; Adapted from split-sequence.
  
negative.code:               for right of-type array-length
                  = (min (or (position-if #'whitespacep s2 :start left) length)
                         end)
                    thereis (and (not (= right left))
                                 (compare-segment left right))
                until (>= right end))))))
  
  (assert (string^= "foo" "foobar"))
  