Hi, I would like to point out that the four built-in variables ($url, $path, $host, and $origin) that can be used during the filter process are not found in the user manual (at least, I wasn't able to find them.) Since they are quite useful, I thought you might want to update the documentation to include them.
Thanks for the report.
Dynamic variables (and other options that aren't inherited from PCRE) are currently documented in default.filter.
I agree that they deserve to be mentioned in the filter section as well and will look into this.
Can you tell me how to use these variable?(Oh, sorry for bothering...)Last edit: Jak Wings 2014-10-17
The documentation has been extended a while ago:
http://www.privoxy.org/user-manual/filter-file.html