Defining named regular expressions using nested let statements.

If I define a named regexp using nested let statements I get an error when trying to use it.

For example:

let int_lit =
  let digit = [%sedlex.regexp? '0'..'9'] in
  [%sedlex.regexp? Plus digit]

Then later on:

match%sedlex buf with
| int_lit -> ...

Sedlex: unbound regexp int_lit.

I've noticed this same problem. In general let ... in seems fragile for some reason.