I'd like my FindProxyForURL() to recommend a different proxy depending on the HTTP-method of the request -- GET, POST, or PUT.
For example, the GETs can be routed through a caching proxy, whereas the POSTs and the PUTs would go DIRECT... Or someone may prefer to add security to their submissions by routing the POSTs through Tor, but without slowing down the regular -- GET-based -- browsing.
The standard PAC-functions provide no mechanism for this, but, maybe, Firefox (or Chrome?) do offer some sort of extension?
