Thanks, that's very helpful and may well be the encouragement I apparently needed! It is a standalone CLI application but it might want to offer a library in the future. And in any case I am attracted to following your suggestion regarding custom enums, partly because it seems more likely to dispel my lack of understanding of the topic.
Cheers! It's a daunting topic with many different ways of doing things and it is difficult to find reading material on the topic of idiomatic error handling. I just read through a lot of popular code bases and picked out what I liked. I found that using custom errors was the simplest approach for me albeit a little verbose.
