anchor.diff:    (defcmp (string~= string-tokenp) (s1 s2)
       "Does S1 occur in S2 as a token?
   
  -This is equivalent to
  +Equivalent to
        (find S1 (tokens S2) :test #'string=),
   but without consing."
       ;; Adapted from split-sequence.
  
positive.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"))
  
negative.code: 
  This is similar, but not identical, to SEARCH.
  
       (search nil \"foo\") => 0
       (search \"nil\" \"nil\") => 0
       (string*= nil \"foo\") => NIL
       (string*= nil \"nil\") => T"
      (call search s1 s2))
  