Client for https://github.com/Yubico/yubikey-val/wiki/ValidationProtocolV20 https://github.com/Yubico/yubikey-val/wiki/GettingStartedWritingClients https://github.com/Yubico/yubikey-val/wiki/ClientInfoFormat https://github.com/Yubico/yubico-perl-client/blob/master/lib/AnyEvent/Yubico.pm