Regular Expressions, LIKE, and indexes

From everything I've been able to find, it seems that the only way to get
front-anchored regular expressions or LIKE patterns beginning with constants
to use an index is to have previously initialized your database using the C
locale. Is this still true? I'm trying to do something like:

SELECT keyword FROM keywords WHERE keyword ~ '^foo';

or

SELECT keyword FROM keywords WHERE keyword like 'foo%';

Are there any other functions that can provide equivalent results while
using an index, or am going to have drop UTF-8 and recreate my database?

Thanks,
Travis