Fails ...

GET https://account.guildwars2.com/oauth2/token?grant_type=authorization_code&redirect_uri=http%3A%2F%2Flocalhost%3A3000%2Foauth2%2Fcallback&client_id=gw2_api_demo&client_secret=[REMOVED]&code=[REMOVED] HTTP/1.1
Connection: Keep-Alive
Authorization: Basic [REMOVED base64 encoding of client_id:client_secret]
Host: account.guildwars2.com:443
User-Agent: libwww-perl/6.13

Works ...

GET https://account.guildwars2.com/oauth2/token?grant_type=authorization_code&redirect_uri=http%3A%2F%2Flocalhost%3A3000%2Foauth2%2Fcallback&client_id=gw2_api_demo&client_secret=[REMOVED]&code=[REMOVED] HTTP/1.1
Connection: Keep-Alive
Authorization: Basic [REMOVED]
Host: account.guildwars2.com