For the original implementation of delimited continuations, see 

http://hackage.haskell.org/package/CC-delcont-0.2

The code is here: 

main : http://hackage.haskell.org/package/CC-delcont-0.2/docs/src/Control-Monad-CC.html#runCC

Prompts : http://hackage.haskell.org/package/CC-delcont-0.2/docs/Control-Monad-CC-Prompt.html

Sequence : http://hackage.haskell.org/package/CC-delcont-0.2/docs/src/Control-Monad-CC-Seq.html