urlrewrite-3.1.0,多参数传递的问题

Question

urlrewrite.xml中作如下配置:    
    <rule>
            <from>/gsjbxx/([a-z][0-9]*[A-Z])-preAdd-([a-z][0-9]*[A-Z])</from>
            <to>/jsp/gsjbxx/gsjbxxAdd.jsp?a=$1&b=$2</to>
    </rule>
然后用http://localhost:8080/gsjbxx/sS-preAdd-kK访问,总是找不到!
而将to中只传一个参数,都能正常得到,为什么呢？
传两个参数如何传?