Coincidentally just saw this video a few days ago.

Interesting approach, to use RPN for expressions, including for the condition in the while statement.

I could understand most of the logic of the interpreter, except for the part about how the while statement is implemented.

I did not quite understand the parts of the code with

  case "while" 

  case "end

That is, around the region of lines 11 to 14 or so, at about 18:0 in the video.

How does the code there, work?