Lookup and mimic the system proxy settings on Windows as set by Internet Explorer. This can be used to configure curl to use the same proxy server.
ie_proxy_info()ie_get_proxy_for_url(target_url = "http://www.google.com")
url with host for which to lookup the proxy server
The ie_proxy_info function looks up your current proxy settings as configured in IE under "Internet Options" under "LAN Settings". The ie_get_proxy_for_url determines if and which proxy should be used to connect to a particular URL. If your settings have an "automatic configuration script" this involves downloading and executing a PAC file, which can take a while.