SW> (let ((test "hello world"))
      (cl-who:with-html-output-to-string (s nil :indent t)  
        (:html (:body (:h1 (str (format nil "hehe ~A" 19)))
                      (:h1 (fmt "hehe ~A" 19))
                      (:h1 (str test))
                      (:h1 (fmt "test: ~A" test))))))
"
<html>
  <body>
    <h1>hehe 19
    </h1>
    <h1>hehe 19
    </h1>
    <h1>hello world
    </h1>
    <h1>test: hello world
    </h1>
  </body>
</html>"