Hello! I'm the creator of Gleam.

> It seems to be a direct riff on Haskell's "do notation" syntax sugar

It's not this at all! It may seem this way at first as Gleam's `use` is used in many of the same places as Haskell's `do`, but `use` is a much more general syntax which is used for a much wider array of things. They also work very differently, `do` being constrained by types and laws, while `use` being purely a syntactic feature with no type restrictions or laws.