Pacparser is a library to parse proxy auto-config (PAC) files. Proxy
auto-config files are a vastly used proxy configuration method these
days. Web browsers can use a PAC file to determine which proxy server to
use or whether to go direct for a given URL. PAC files are written in
JavaScript and can be programmed to return different proxy methods
depending upon URL, source IP address, protocol, time of the day etc.
PAC files introduce a lot of possibilities.