Look at it closely - it's exactly the same as your OCaml example, except it uses ";" instead of "in", and indentation is adjusted accordingly.

Although in practice I found that it's common to not indent adjacent nested let..in blocks in OCaml, either, so you'd often see something like:

  let foo = "..." in
  let foo = parse(foo) in
  let foo = escaped(foo) in
  ...

And the rules are really simple - "let" always introduces a new binding.