reader extension

[Felix S Klock II <pnkfelix at MIT dot EDU>]

Is there an easy way to extend/modify Kawa's reader within pure scheme
code?  

I mainly want to change how Kawa handles reading certain constructs
while working within a particular REPL.  This particular language uses
"#u" to stand for the single element of type Unit, not as the begining
of some vector object as it seems to be setup currently in Kawa.  This
is only one example of a change I need to make, though it is the most
immediately pressing one.  (Distinquishing square bracketed
expressions from parenthesized ones is the other issue, but I'm not
really concerned with that right now)

Unfortunately, I am not terribly familiar with what has been done in
the past w.r.t. this problem, like Common Lisp's readtables or
whatever.  It doesn't seem to me that Scheme has a standardized way to
extend/change the reader.

If anyone has any suggestions I'd like to hear them.  Of course, I
realize that an obvious answer is "hack up some java code extending
Kawa for your particular language" but I would like to believe that
Scheme-like languages would have a more Schemey path for support.  C:P 

Thanks

-Felix