This is another note to myself. For some reason I have a hard time remembering the handful of commands that do things to the lines in a buffer that match a regular expression. The table below are the ones that I know about but have a hard time remembering. If you have any similar commands that you find useful, leave a comment.
|keep-lines||delete-non-matching-lines||Delete lines not matching regexp|
|flush-lines||delete-matching-lines||Delete lines matching regexp|
|how-many||count-matches||Count lines matching regexp|
|occur||list-matching-lines||Show lines matching regexp in another buffer|
|highlight-lines-matching-regexp||hi-lock-line-face-buffer||Highlight lines matching regexp|
Update Phil reminds me of
highlight-lines-matching-regexp, which I meant to include but forgot. (See what I mean?) He also mentions
multi-occur (just like
occur but it acts on multiple buffers) and
multi-occur but you specify the buffers with a regexp), which he says he finds particularly useful.