anchor.diff:           `(%nconc (copy-list ,(let tr *transpiler*
                                   (? (transpiler-assert? tr)
                                      (frontend-macroexpansions `(aprog1 ,(cadr x.)
  -                                                                (| (list? !) (error ",@ expects a list instead of ~A." !))))
  +                                                                (| (list? !)
  +                                                                   (error ",@ expects a list instead of ~A." !))))
                                      (cadr x.))))
                      ,(backquote-1 .x))
            (cadr x.))))
  
positive.code: ;;;;; tré – Copyright (c) 2006–2013 Sven Michael Klose <pixel@copei.de>
  
  (defun backquote-quasiquote (x)
    (? (any-quasiquote? (cadr x.))
       `(cons ,(backquote-1 (cadr x.))
              ,(backquote-1 .x))
       `(cons ,(cadr x.)
              ,(backquote-1 .x))))
  
  (defun backquote-quasiquote-splice (x)
    (? (any-quasiquote? (cadr x.))
  
negative.code: (defun backquote-1 (x)
    (?
      (atom x)                (quote-literal x)
      (atom x.)               `(. ,(quote-literal x.)
                                  ,(backquote-2 .x))
      (quasiquote? x.)        (backquote-quasiquote x)
      (quasiquote-splice? x.) (backquote-quasiquote-splice x)
      `(. ,(backquote-1 x.)
          ,(backquote-2 .x))))
  
  (defun simple-quote-expand (x)
    (? (atom x)
       (quote-literal x)
       `(. ,(simple-quote-expand x.)
           ,(simple-quote-expand .x))))
  
  (defun backquote-expand (l)
    (tree-walk l
  