Storing regular expressions somewhere....

[Birju Prajapati]

Hi all,
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?

TIA
Birju