I don't know if it possible to do that with st directly, but you simply could add code to rewrite url if it met for some cases.
ad code like
var exceptions = {
'wrong_path':'right_path'
}
function rewriteUrl(req){
if(exceptions[req.url]){
req.url = exceptions[req.url];
}
}
and then call that function before st method calling
http.createServer(function (req, res) {
rewriteUrl(req);
mount(req, res);
}).listen(1234);