static IEnumerable<IEvent> Proc(IEnvironment env)
{
var ev1 = env.Event();
env.Start(DoSucceed(env, ev1));
yield return ev1;
if (ev1.Succeeded)
Console.WriteLine(ev1.Value);
var ev2 = env.Event();
env.Start(DoFail(env, ev2));
yield return ev2;
if (ev2.Failed)
Console.WriteLine(ev2.Value);
}
