how to do an XOR Stencil in Unity?

I'm trying to make geometry only render when inside another piece of geometry. Like if you had a Sphere partially intersecting a Cube, only the part of the sphere inside the cube would be visible.

I've seen another post which says to use an XOR Stencil... but I can't find any information about how to write an XOR stencil.

can anyone help?

 

https://alastaira.wordpress.com/2014/12/27/using-the-stencil-buffer-in-unity-free/

or even the official documention should be enough

http://docs.unity3d.com/Manual/SL-Stencil.html

post your progress