I do agree that the RealWorld stuff is there to enforce control flow, but that is exactly one of the things that we needed. I also realise that the modern GHC o

I do agree that the RealWorld stuff is there to enforce control flow, but that is exactly one of the things that we needed. I also realise that the modern GHC optimizes such things away, so there is no RealWorld! Regards implementation, as the type system available in XQuery is much more limited than that of Haskell, I had to choose some mechanism to represent an IO. Actually representing it as a state transforming function that operates on the RealWorld, as was done in the design of the IO Monad for Haskell, seems to work pretty well. I tried to follow closely and adapt both: 1) Section 7.3 "Monadic I/O" from "A History of Haskell", Hudak, Hughes, Peyton Jones and Wadler 2007 - https://www.microsoft.com/en-us/research/wp-content/uploads/2016/07/history.pdf https://www.microsoft.com/en-us/research/wp-content/uploads/... 2) Section 4 "Implementing monadic I/O" from "Imperative functional programming", Wadler and Peyton Jones 1992 - https://www.microsoft.com/en-us/research/wp-content/uploads/1993/01/imperative.pdf https://www.microsoft.com/en-us/research/wp-content/uploads/...