On the off chance your finding this from Étude 12-1 from Études for Elixir, here's what ended up working for me
s_url = "http://w1.weather.gov/xml/current_obs/"<> weather_station <> ".xml" :httpc.request(:get, { to_char_list(s_url), [ {'User-Agent','ErlangEtudes/v1.0 (http://example.org;me@example.org)' } ] },[],[] )