DSL design (was DSLs in perl and python)

[Jussi Piitulainen]

Rustom Mody writes:

> [How BTW did you folks go about unearth that groupindex?? Dont see it
> in docs]

The following reveal its existence:

dir(re.compile(""))
help(re.compile(""))

But help only lists it as one of "data descriptors defined here" (in
Python 3.4.3). I think I just guessed from its name that it might be
relevant, and trying it out didn't immediately contradict the guess :)