Sometimes green threads require no syntactic featutes at all, e.g. Lua coroutines. You yield() through the stack and resume() back when “done”.

  local data = readfile("file1”)
  writefile("file2", data)

The above example may have async/await-ed two times without any sugar. I believe that’s exactly what coop-mt code would look like (but at the lower level, because of hw stack instead of heap-based), Tbf I never did that in windows 3.x, do I miss something?