jndi-taglib and scripting variables

Hi all,

I have a portal with a jsp channel in which I use the jndi-taglib. I'm 
trying to do a ldap-search with the portal user's userid. I get the id 
from elsewhere and both

<jx:expr value="$userid" />   and
<%=userid%>

print it out just nice. However, when I try

<jndi:search id="searchResult" contextRef="ldapContext" 
filter="uid=<%=userid%>" searchScope="subtree" >
</jndi:search>

or filter="uid=<jx:expr value="$userid" />" things don't work the way they 
should. With <jx:expr> it says

com.sun.portal.providers.jsp.jasper3.jasper.compiler.ParseException: 
/etc/opt/SUNWps/desktop/*/*/content.jsp(31,91) Attribute 
$userid has no value

and with <%=userid%> I just get an empty searchResult. It surely must be 
possible to give the id as a parameter to the filter somehow? Any ideas?

Iikku