I failed miserably. My capturing groups didn't work. Then my digit character classes didn't work either. I was stunned.. what was I doing wrong?

Then I stumbled on Steve Yegge's emacs reg-exp post, where explains all of those limitations:

    *  You have to escape the (, ), {, }, and | metacharacters. That is, they're not metacharacters by default — without the backslash, they match themselves.

    * There's no '\d' shortcut for the [0-9] character class.

    * There are no lookahead or lookbehind assertions.

    * There are no direct equivalents for Perl's {n}?, {n,}?, {n,m}?, /i, /m, /s, /x, \G, or (?# ...) constructs.

while usually you'd match: (public Relative)(\w)(\w+)

I really must say that I was surprised that, being such a killer editor, we as a community never got round to implementing a modern regexp syntax for emacs.

Is it that hard? Do many people miss this? ..or you eventually get used to the old syntax and skipping everything?

http://steve-yegge.blogspot.com/2006/06/shiny-and-new-emacs-22.html