buffer question

Hi.

I'm new to writing shaders, so I hope i wont ask something stupid.

I've played with some basic fragment shaders, and I've managed it to work as screen effects.

Now... there is something that i don't understand...
there is shader in https://www.shadertoy.com/view/4dK3Ww# where it uses buffers.
How do I implement this in Unity shader?
Do I have to use multiple passes and Graphics.Blit or maybe GrabPass?

Hope someone can help me.

best regards

 

I hope i'm not to late with an answer
here is what you are looking for
http://www.alanzucconi.com/2016/03/02/4539/