The dot (.) in the filter rules is used to match any character. So for example ....foo.bar matches www.foo.bar and www.foo.bar would also match wwwxfooybar. This should be better documented, since it's not what a naive user would expect, and they might accidentally allow or block domains unintentionally. To correctly block/allow www.foo.bar you would need to set www\.foo\.bar.

I would actually prefer it to be simpler. I think fnmatch() could be used instead of regexc().