\_ I have found the 'replace-string' and 'replace-regexp' in EMACS, and I use
\_ them a lot.
\_ 
\_ Unfortunately, replace-regexp only allows you to use a fixed replacement
\_ string.
\_ 
\_ How do I interactively replace a regexp with a regular expression?

Hmmm...teach to fish or provide fish....

M-x apropos regexp   ; learn to fish

Paging the resulting set will make you go "do'h" if you've used the
interactive search and replace for standard boring regexps (those with
no wild cards, also known as just 'search').

David