Remembering a regexp across searches

[Michael Preminger]

Hello!

Maybe something I would expect to find in the FAQ, but to no avail:

I need to do repeating incremental searches of regular expression.

when I find what I was looking for - I need to do some changes 
(manually), and then search for the next occurrence corresponding to the 
same regexp.

Sometimes the regexps are complicated, and retyping them in the 
Iserach-buffer is tedious.

How do I avoid this re-typing? Is there a way to make emacs "remember" a 
regexp and re-use it in a handy way?

Thanks

michael