Thanks for the pointer to `cmdliner`. I've built a handful of command line tools using Command from the Core library (as described by Real World OCaml [1]), but I always have to have the book open to use it. This looks very nice and it looks like it might fix an annoyance I have with Core's `Command`, which is that it won't parse flags without spaces (i.e., `-r2` failes to parse as equivalent to `-r 2`).

[1] https://realworldocaml.org/v1/en/html/command-line-parsing.h...