Request Time (RT) expressions being treated as literals in Tomcat 4.x

Because I have to use Tomcat 4.x, I am using RT expressions to
dynamically populate the attributes of my custom tags:

<myTag:sayHello name=<%= request.getParameter("userName") %>" />

Can anyone tell my why the RT expression is being treated as a literal?
All my tag is supposed to do is take the name attribute and write it
back to the browser (like "Hello Brian", for example).

Instead it prints back:

"Hello <%= request.getParameter("userName") %>"

Any suggestions?

thanks

-- brian