proxy.cfg  define proxies for each destination and port.

The path specified by PROXY_CFG environment variable overrides the
default compilation time value (usually /etc/proxy.cfg)

Format

eg
	# First match wins
	#[!]destination		[!]dest-ports	proxy-def	auth
	172.17.234.0/16		80,8080		proxy.example.com:3128	-
	192.168.128.0/18	!443		172.31.0.254:8080	-	
	10.0.0.0/8		80-88		gw.xor.com:1080		-

The rules in proxy.cfg are prefixed by 

	# no proxy for ourselves
	127.0.0.0/8	*	direct	-
	0.0.0.0/32	*	direct	-

and suffixed by 

	# all else fails fall back to direct
	*	*	direct	-