uClibc regex

[Tony Lin]

Greetings list.

Is it possible to match on nth instance of a marked subexpression? For
example, with the string:

"hello _world_ !!!"

I would like to extract the world "world". The closest I can get to is
using the regex expression:

"_(.*)_"

This gives me two subexpression matches
1. "_world_"
2. "world"

I can't seem to be able to select the 2nd subexpression using
"_(.*)_\2", I guess it's not supported?

Thanks.