Useful RE patterns (was: Variable Interpolation - status of PEP 215)

[nntpserver.pppl.gov]

Fredrik Lundh wrote:
> If I were to add a dozen (or so) patterns to the (S)RE module,
> what should I pick?  What patterns do you find yourself using
> over and over again?

Most of the time whenever I use regexes I'm trying to solve
specific problems.  But what comes to mind are lexers-token-like
patterns: identifiers, numbers (ints, floats), strings (yes,
know :-)
They don't have to be _perfect_ to be useful.  In fact, laziness
takes me to steal them from other places.

Regards,
-Hernan