#lang racket

(define ++ string-append)
(define (html id)
    (begin
      (set! id (symbol->string id))
      (define otag (++ "<" id ">"))
      (define ctag (++ "</" id ">"))
      (lambda children (++ otag (apply ++ children) ctag))))

(define-syntax %%
   (syntax-rules (list begin)
       ((%% id (begin child ...)) ((html `id) child ...))
       ((%% id (list opt ...)) (++ ((html `id) opt) ...))
       ((%% id expr) ((html `id) expr))))

(%% ul (begin "hello" "there"))
(%% ul (list "hello" "there"))