Thinking more...

import System

class MyException(Exception):
  _msg as string
  def constructor( s as string ):
    _msg = s
  override def ToString() as string:
    return "MyException::${_msg}"

// 試著調整這兩個變數試試看
isExceptionHappen = false
isMyExceptionHappen = true

try:
  // .. do something ...
  if isExceptionHappen:
    raise Exception("Something wrong.")  // 提出例外情況
  // ...
  if isMyExceptionHappen:
    raise MyException("Hey!!")
except e as MyException:
  print e.ToString()
except e as Exception:
  print e.Message
ensure:
  print "不管有沒有錯誤，這裡都會被執行。"