(defun Buffer-menu-grep-match (str)
  (interactive "P")
  (call-interactively 'ibuffer)
  (save-excursion
    (goto-char (point-min))
    (let (lines)
      (forward-line 2)
      (setq lines (buffer-substring (point-min) (point)))
      (while (re-search-forward str nil t)
        (let ((bol (progn (beginning-of-line) (point)))
              (eol (progn (forward-line) (point))))
          (setq lines (concat lines (buffer-substring bol eol)))))
      (let ((buffer-read-only nil))
        (erase-buffer)
        (insert lines)))))

(defun Buffer-menu-grep-reject (str)
  (interactive "P")
  (call-interactively 'ibuffer)
  (save-excursion
    (goto-char (point-min))
    (let (lines)
      (forward-line 2)
      (setq lines (buffer-substring (point-min) (point)))
      (forward-line 1)
      (while (re-search-forward ".+$" (line-end-position) t)
        (let ((bol (progn (beginning-of-line) (point)))
              (eol (progn (forward-line) (point))))
          (if (not (string-match str (buffer-substring bol eol)))
              (setq lines (concat lines (buffer-substring bol eol))))))
      (let ((buffer-read-only nil))
        (erase-buffer)
        (insert lines)))))

(defun Buffer-menu-grep-texi ()
  (Buffer-menu-grep-match "texi"))

(defun Buffer-menu-grep-el ()
  (Buffer-menu-grep-match "\\(scratch\\|\\.el\\)"))

(defun Buffer-menu-grep-2ch ()
  (Buffer-menu-grep-match "navi2ch"))

(defun Buffer-menu-grep-default ()
  (Buffer-menu-grep-reject "\\(texi\\|navi2ch\\)"))

(defvar my-buffer-menu-list '(
                              ("\.texi" . Buffer-menu-grep-texi)
                              ("navi2ch" . Buffer-menu-grep-2ch)
                              ("\.el" . Buffer-menu-grep-el)
                              ("." . Buffer-menu-grep-default)
                              ))

(defun my-buffer-menu (arg)
  (interactive "P")
  (if arg
      ;;(call-interactively 'buffer-menu)
        (call-interactively 'ibuffer)
    (let ((alist my-buffer-menu-list)
          (case-fold-search t)
          (buffer-menu-com nil)
          (name (buffer-name (current-buffer))))
      (while (and (not buffer-menu-com) alist)
        (if (string-match (car (car alist)) name)
            (setq buffer-menu-com (cdr (car alist))))
        (setq alist (cdr alist)))
      (if buffer-menu-com
          (funcall buffer-menu-com)
        (call-interactively 'ibuffer)))))

(global-set-key "\C-x\C-b" 'my-buffer-menu)