+[ --enable-extended-host-patterns Enable and require PCRE syntax in host patterns. This feature hasn't
+ been announced yet and it's not clear if it's a good idea. It's expected
+ to work, but undocumented. You should only enable it if you know what
+ PCRE is and are sure that you need it for your host patterns. You can
+ use tools/url-pattern-translator.pl to convert existing action files to
+ use PCRE host patterns. Please don't enable this option when creating
+ packages for others that may not be expecting it.],