How do you add several tasks in once

Often I want to add several tasks I got under the form of a list :
- task1
- task2
- task3

I want to add this tasks as a subtask to an existing one. How can I do ? Idealy, I would like to be able to paste the list in my current task and press enter (with the cursor at the end of the last item), gtg detecting all tasks backward and creating the subtasks.

Note that a current possible work around is to use a shell command parsing the list and feeding gtg_new_task