!! +var+ +exec+ +string+
tit:append
type:$type_both
syntax:!append `object s1' to `str'
mean:串操作: 把对象 `s1' 接在串\
  `str' 的后面. `object' 可以是 `item',\
  `word' 或 `line'. `s1' should not be empty before evaluation.
