In that same vein (or in the vein where I have my coffee injected)...

The things for which I'm always going back to "perldoc perlre" are:

(?=) positive look-ahead
(?!) negative look-ahead
(?<=) positive look-behind
(?<!) negative look-behind
[download]

In fact, I had to look them up again just now, to make sure I posted them right. (Having done this, maybe I'll be able to use them from memory next time.) These really are tremendously useful, and it would be swell to have them visible on my desk at all times (except when I'm drinking my coffee, of course).

I'm reluctant to suggest removing anything you have already, and I suppose you'd need to shrink the font if possible (and abbreviate "positive" and "negative") to make more stuff fit. If that were doable, and you ended up with enough room for just a couple more things besides "[pn].* look-.*d", you could add:

\p{...}  unicode class ...
[:...:]  posix class ...
[download]

(not much detail there, admittedly, but just getting the terms "unicode" and "posix" onto the mug seems worthwhile).