It's entertaining that there is yet another area where "running large numbers of regular expressions, known in advance and not changing all that often" over lots of input is performance critical.

This was a key driver behind writing Hyperscan (https://github.com/intel/hyperscan) which I used to work on when it was primarily used for network security (thousands or tens of thousands of regular expression rules for firewalls), but doing this for ad blocking seems pretty sensible too.