RE: Storing regular expressions somewhere....

[Drew Adams]

    Sometimes I need to do complicated replace-regexps. However, they can
    be prone to errors, so what I end up doing is an
    isearch-forward-regexp until I get the expression correct. Once it is
    correct, I write it down and then type it back into a replace-regexp
    command! Rather cumbersome....Is there some sort of
    isearch-forwared-replace-regexp command ? Or can I recall the previous
    regexp searched for in my isearch-forward-regexp?

You might want to take a look at Icicles, which lets you use `C-=' to recall
a string (e.g. a regexp) that you've saved in a variable, into the
minibuffer later as input. Here's an explanation:

http://www.emacswiki.org/cgi-bin/wiki/Icicles_-_Inserting_a_Regexp_from_a_Va
riable

HTH.