[dnsdist] regexrule for ipv6-PTR-queries (ipv6-subnet)

[Tom]

Hi list

I'm trying to route ipv6-ptr-queries for the net "2001:db8:7000::/36" to 
our knot. This should cover all v6-adresses for "2001:db8:7*".

I've configured the following regexrule:

addAction(AndRule({RegexRule(".*\.7\.8\.b\.d\.0\.1\.0\.0\.2\.ip6\.arpa$"), 
QTypeRule(DNSQType.PTR)}), PoolAction("knot"))

Currently, the queries are only matching like this:
dig @server -x 2001:db8:7000::1 -> OK
dig @server -x 2001:db8:7000::14 -> OK
dig @server -x 2001:db8:7000::cafe -> OK

dig @server -x 2001:db8:7001::1 -> failed, not matching knot-pool
dig @server -x 2001:db8:7002::1 -> failed, not matching knot-pool
dig @server -x 2001:db8:7999::1 -> failed, not matching knot-pool
dig @server -x 2001:db8:7abc::1 -> failed, not matching knot-pool
dig @server -x 2001:db8:7abc::cafe -> failed, not matching knot-pool

Any hints what's wrong with the regex above? How can I catch the 
PTR-queries for "*.7.8.b.d.0.1.0.0.2.ip6.arpa."?

Many thanks.
Kind regards,
Tom