Just a note that Crayon 1.9.8 adds support for Haskell, and also TeX.
module Interpret(interpret) where

import Prog

import System.IO.Unsafe
import Control.Monad
import Char

-- In a call to this function such as "interpret prog vars entry debug":
-- prog is the ABCD program to be interpreted;
-- vars represents the initial values of the four variables;
-- entry is the name of the entry point function, "main" by default; and
-- debug specifies whether the user wants debugging output.

interpret :: Prog -> Vars -> String -> MaybeDebug -> IO ()
interpret prog vars entry debug = do
    let context = Context prog vars entry debug 0
    let newContext = runFunc entry context
    let output =
        case newContext of
            IError s -> "abcdi: " ++ s
            IOK c -> (strVal (getVar A (cVars c))) ++ "\n"
    putStrLn output