gistfile1.txt

#lang racket

(require syntax/parse/define
         (for-syntax syntax/parse
                     racket/base
                     racket/syntax))

(define-syntax-parser foo
  [(_ headers ... body ...)
   #:when (for/fold ([good? #t])
                    ([i (in-list (attribute headers))])
            (define still-good?
              (or (identifier? i)
                  (and (string? (syntax-e i))
                       (regexp-match  "^ $" (syntax-e i)))))
            (and good? still-good?))
   (writeln (attribute headers))
   (writeln (attribute body))
   #'42])

(foo a " " b "\n" c)