In the example on how to convert parseCommand into using do notation, the following snippet:

parseCommand schema "schema" rest
 = do schemaok <- parseSchema (words rest) of
 Just (SetSchema schemaok)

should read

parseCommand schema "schema" rest
 = do schemaok <- parseSchema (words rest)
 Just (SetSchema schemaok)

There is a leftover "of" from the case statement

Thanks, this is fixed now