For inspiration how to handle `no_proxy`, as well as see how Ruby handles these environment variables, see the [URI#find_proxy method](https://github.com/ruby/ruby/blob/8f04556111b25d336838f40aaed34b86a44c9470/lib/uri/generic.rb#L1600-1673)

An interesting detail from this code is that it gives precedence to lowercase variables rather than their uppercase versions. Don't know the reasoning behind it.