gistfile1.el

(defun my-change-log-extract (regexp)
  "Extract the entries that matches to the regexp in change-log-mode"
  (interactive "sregexp: ")
  (goto-char (point-max))
  (do ((expression "^[0-9]\\{4\\}-[0-1][0-9]-[0-3][0-9]")
       (pos (point) (point))
       (list nil (cons
                  (cons 
                   (match-string 0)
                   (buffer-substring (match-beginning 0) pos)) list)))
      ((not (re-search-backward expression nil t))
       (with-output-to-temp-buffer "*Extracted*"
         (switch-to-buffer "*Extracted*")
         (mapc (lambda (item)
                 (if (string-match regexp (prin1-to-string (cdr item)))
                     (insert (cdr item))))
               list)))))