[arch-general] Setting global environment variable

[Ty John]

I'm regularly connecting and disconnecting to a VPN using vpnc. The
network I connect to has a transparent proxy which I want to set
$http_proxy to.
I thought I could do something like

export http_proxy="proxy.whatever.com"

in the /etc/rc.d/vpnc file, in the start and stop functions as
necessary but exporting only makes the variable available to the child
processes. Not to mention, I need this variable set for normal users
also.

Basically, I want to set and unset the variable when I connect and
disconnect the VPN.

Any ideas?