non-perl5 regexes and greppable

[AlexDaniel]

Quotable accepts Perl 6 regexes, but Greppable takes pcre stuff. Dog fooding to the max, everything should use Perl 6 regexes, even if it is a little bit slower.

At least, we can start with an option and see how it goes.

[AlexDaniel]

For example, this will let users to control case sensitivity from within the regex, without learning any special bot syntax.