intersperse package:io-streams

The function intersperse v s wraps the OutputStream s, creating a new output stream that writes its input to s interspersed with the provided value v. See intersperse. Example:

ghci> import Control.Monad ((>=>))
ghci> is <- Streams.fromList ["nom", "nom", "nom"::ByteString]
ghci> Streams.outputToList (Streams.intersperse "burp!" >=> Streams.connect is)
["nom","burp!","nom","burp!","nom"]