It's a good description of one application of monads, which is often helpful to beginners if they have been thrown into real code without yet understanding the

It's a good description of one application of monads, which is often helpful to beginners if they have been thrown into real code without yet understanding the "why" of monads. If you look up "railway-oriented programming," you'll find more presentations of it. I think it is a very practical place to start, especially for programmers who have been thrown into a codebase while still new with monads, because it helps them avoid a common mistake that plagues beginners: accidentally dropping error values on the non-success track. Often you simply want to drop values on the non-success track, and there are convenient idioms for doing so, but just as often, you need to examine those values so you can report failures, by returning metrics on validation failures, by providing the right status code in an HTTP response, etc. Railway-oriented programming is a vivid metaphor that reminds programmers that they need to make a decision about how to handle values on the other track.