>>53
C-u C-s/C-r
(add-hook 'isearch-mode-hook
(lambda ()
(define-key isearch-mode-map "-"
(if isearch-regexp
(lambda () (interactive)
(setq isearch-string (concat isearch-string "[_-]")
isearch-regexp isearch-string
isearch-message isearch-regexp)
(isearch-search-and-update))
'isearch-printing-char))))