Dynamic/animated linking, through constraints:

Quite often people ask if it is possible to 'animate linking'.
Though almost anything is possible through mel, this is not the way to do it.

What you should use was a 'point' and an 'orient' constraint.

What I usually do is that I link/place locators at each 'state'
i.e: then hand and the mouth, then 'point' and 'orient' constrain the object to all the locators.
Now you can animate the 'weights' of the constraints to make the object follow/align with the locators.

I have a small example of a guy walking with his sword in his hand, then holding it with his teeth and then back in his hand.