问题
我们知道Emacs Lisp并不像其他语言那样有return语句。那么，如果我想在程序的任意位置返回，那该如何做呢？
使用catch机制
有一种方法是，采用catch机制，下面是一个例子：
(defun lebe-fun-exit-any-arbitrary-point ()
"Example show how to exit from a function at any arbitrary point in elisp."
(interactive)
(let ((a "a"))
(catch 'return
(when (equal "a" a)
(throw 'return "non-local exit value"))
(message "normal exit value"))))
执行下看：
ELISP> (lebe-fun-exit-any-arbitrary-point)
"non-local exit value"
