i'd better avoid using regexps in content blocker: they aren't *that* good in early rejecting, but slower and more memory-demanding. i think it is better to calculate b-m-like «substring presence» tables for patterns, and b-m table for url before checking. b-m table for urls can be cached in the content blocking module, btw, but i don't think that it is really worth the efforts: «domain as key» will take care of most rejects, i believe.