Returning a top-level export instead of as part of a table

[s5bug]

How to emulate

return function(importantArgData)
  return { stuff = "stuff" }
end

in Amulet? The best that I can do is generating a table with --export:

let foo importantArgData = { stuff = "stuff" }

do
  return { foo = function(importantArgData) return { stuff = "stuff" } end }
end

[s5bug]

What would be the best way to handle this? --export looking for an expression at the end of the file instead of exporting all top-level declarations? I.e.

let foo = ???
let bar = ???

function (x : int) -> foo (bar x)

is a valid Amulet file?

More likely there's a better way, but I haven't been able to think of it.