Canonical examples for how to use `andThen`

[markd2]

Hi! It'd be nice to have canonical examples on how to use andThen. There was recently an extended Slack chat about using andThen, with suggestions about defeating type inference, the use of try causing odd errors, and then questions on how to propagate errors out in to the result that anyone who upons peels apart. It'd be nice if there were a canonical example of its use we can crib from and expand. andThen is mentioned a couple of times in the intro docs, but not an actual use that I could find.