(tree-case *args*
  ((big small)
   (cond
     ((< (length big) (length small))
      (put-line `@big is shorter than @small`))
     ((str= big small)
      (put-line `@big and @small are equal`))
     ((starts-with small big)
      (put-line `@small is a prefix of @big`))
     ((ends-with small big)
      (put-line `@small is a suffix of @big`))
     (t (iflet ((pos (search-str big small)))
          (put-line `@small occurs in @big at position @pos`)
          (put-line `@small does not occur in @big`)))))
  (otherwise
    (put-line `usage: @(ldiff *full-args* *args*) <bigstring> <smallstring>`)))