It can be used to teach people how concepts from one language map to another. For example, from Python to Elm.
The top box contains source text. The left box below it is the matching rule, and the box right to it is the replacement rule. The blue border box is what
comby found, and the red border box contains the result of transformation. Isn’t it awesome?
Try it yourself - https://bit.ly/2xLpGLG