anchor.diff:                            :direction :output
                             :if-exists :append
                             :if-does-not-exist :create)
  -    (write-string contents stream)
  +    (write-string (replace-vars contents) stream)
       (terpri stream)))
   
   (defun s/r (file search replace &key (all T) case-insensitive single-line multi-line)
  
positive.code:                           :direction :output
                            :if-exists :rename-and-delete
                            :if-does-not-exist :create)
      (write-string contents stream)
      (terpri stream)))
  
  (defun >> (file contents)
  
negative.code: 
  (in-package #:org.shirakumo.autobuild)
  
  (defun %replace-vars (target start end match-start match-end reg-starts reg-ends)
    (declare (ignore start end match-start match-end))
    (let ((op (subseq target (aref reg-starts 0) (aref reg-ends 0)))
          (args (cl-ppcre:split " +" (string-trim " " (subseq target (aref reg-starts 1) (aref reg-ends 1))))))
      (cond ((string= op "path")
             (let* ((project (or (project (first args))
                                 (error "No such project ~s" (first args))))
                    (id (if (string= (second args) "latest") :latest (second args)))
                    (build (or (build id project)
                               (error "No such build ~s" id))))
               (uiop:native-namestring (location build))))
            (T (error "Unknown op ~s." op)))))
  
  (defun replace-vars (string)
    (cl-ppcre:regex-replace-all "\\$\\{([^ ]*)(.*?)\\}" string #'%replace-vars))
  
  (defun $ (cmd)
    (run "bash" (list "-c" (replace-vars cmd))
         :output *build-output* :error *build-output*
         :on-non-zero-exit :error))
  
  