Add this to httpd.conf:
AddType text/shtml .shtml ExtFilterDefine shtml-to-html intype=text/shtml outtype=text/html cmd=/usr/local/bin/shtml2html AddOutputFilter shtml-to-html shtml
Apache serves .shtml-files as HTML; for instance:
(html (p "Harro"))becomes:
<!DOCTYPE html><html><p>Harro</p></html>