How to define an “if else” helper

[R2D221]

Hi, I've recently found this project and I think it's an interesting alternative to Handlebars.

I'm testing some stuff to see how it works, but I can't find the way to set an “if else” helper. Normally in Handlebars this helper is already defined, but its documentation still shows you how it works.

Handlebars.registerHelper('if', function(conditional, options) {
  if(conditional) {
    return options.fn(this);
  } else {
    return options.inverse(this);
  }
});

However, in HTMLBar the API to define helpers is different. You invoke this.yield(); instead. But I can't find a way to tell the yield method to call the else block.

Am I doing something wrong, or is this feature not supported?