Syntax error in ST.hs

I noticed this while going through the SOE book:

$ hugs
__   __ __  __  ____   ___      _________________________________________
||   || ||  || ||  || ||__      Hugs 98: Based on the Haskell 98 standard
||___|| ||__|| ||__||  __||     Copyright (c) 1994-2002
||---||         ___||           World Wide Web: http://haskell.org/hugs
||   ||                         Report bugs to: [email protected]
||   || Version: November 2002  _________________________________________

Haskell 98 mode: Restart with command line option -98 to enable extensions

Reading file "/lusr/lib/hugs/lib/Prelude.hs":
                   
Hugs session for:
/lusr/lib/hugs/lib/Prelude.hs
Type :? for help
Prelude> :load Memo
Reading file "/lusr/lib/hugs/lib/exts/Memo.hs":
Reading file "/lusr/lib/hugs/lib/exts/ST.hs":
Reading file "/lusr/lib/hugs/lib/Array.hs":
Reading file "/lusr/lib/hugs/lib/Ix.hs":
Reading file "/lusr/lib/hugs/lib/List.hs":
Reading file "/lusr/lib/hugs/lib/Maybe.hs":
Reading file "/lusr/lib/hugs/lib/List.hs":
Reading file "/lusr/lib/hugs/lib/Array.hs":
Reading file "/lusr/lib/hugs/lib/exts/IOExts.hs":
Reading file "/lusr/lib/hugs/lib/IO.hs":
Reading file "/lusr/lib/hugs/lib/exts/IORef.lhs":
Reading file "/lusr/lib/hugs/lib/exts/IOExts.hs":
Reading file "/lusr/lib/hugs/lib/Monad.hs":
Reading file "/lusr/lib/hugs/lib/exts/ST.hs":
Parsing
ERROR "/lusr/lib/hugs/lib/exts/ST.hs":49 - Syntax error in type expression (unexpected `.')
Monad> 

I don't know enough about Haskell to figure out what the problem is.
There are at least a couple other modules in the exts directory that
apparently show similar errors: ParsecToken, LazyST.

Am I looking at a bug or did I do something wrong?

Tommy McGuire