In org-mode, a line starting with a colon is formatted as source code. ( http://orgmode.org/manual/Literal-examples.html )
In literate Haskell, source code lines start w
I had essentially the same motivation, to use org-mode markup for my Haskell (Bird style) literate programs. I ended up using multi-mode which allows multiple emacs major modes to be used for different regions in the same buffer (there are others but multi-mode suited my requirements). I cooked up haskell-org which enables org-mode and haskell-mode to be used in a single buffer via multi-mode.
More details in this blog entry. The setup works well enough that I use it for my Haskell coding.