Here is a good example: http://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/emacs-lisp/lisp-mode.el#n430 http://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/

Here is a good example: http://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/emacs-lisp/lisp-mode.el#n430 http://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/emacs-l... DFAs for regular expressions use exponential memory for regular expression size (also exponential time to compile them to DFAs). Try that for the regular expressions in the link above. There is no way to make regular expressions fast.