[Haskell-cafe] [: Where the bracket things are? :]

I'd like to add my own custom list delimiters to ghc; such as the [: and :] of Data Parallel Haskell. The purpose is mainly to learn a little about GHC's internals. Any suggestions on the GHC files I should look at first? Alternatively, maybe this is actually possible from outside the compiler. Cheers, Paul