SXML is an alternative syntax for writing XML data, using the form of S-expressions.
The benefit of SXML is to take advantage of quasiquote in Scheme. If you no little about it, then you may google "scheme quasiquote" for more details.
(tpl->response '(html (body (p (@ (id "content")) "hello world"))))
You would get a html string:
<html><body><p id="content">hello world</p></body></html>
Sometimes you may need quasiquote to reference a variable, for example:
(let ((content "hello world")) (tpl->response `(html (body (p (@ (id "content")) ,content)))))