@(do
   (defstruct header nil
     name
     value
     (:method equal (hdr) hdr.name))

   (defvar custom-headers ()))
@(define headers)
@  (output)
Content-type: text/html;charset=UTF-8
@    (repeat :vars (custom-headers))
@{custom-headers.name}: @{custom-headers.value}
@    (end)

@  (end)
@(end)
@(define replace-header (name val))
@  (do (pushnew (new header name name value val) custom-headers))
@(end)
@(define add-header (name val))
@  (do (push (new header name name value val) custom-headers))
@(end)