Here's how you might write a photo gallery:

(define-dynamic-pages "(.*)\.jpg" "\1.jpg" reader: copy-file)
(define-dynamic-pages "(.*)\.jpg" "\1.thumb.jpg"
 reader: read-jpeg
 renderer: (cut make-thumbnail 16 16 <>))
	(define-page "index"
	 (map (lambda (f)
	       '(li (a (@ (href ,(conc (match 1 f) ".jpg")))
	            (img (@ (src ,(conc (match 1 f) ".thumb.jpg")))))))
	  (file-list "(.*)\.jpg")))