Looks like a nice library, but I'm not in love with the syntax; I find it a bit confusing TBH... But it packs some nice features, specially the validation and precendece awareness. A simple overloading helper works for my needs though, ie: https://gist.github.com/elclanrs/8515458
Thanks for the feedback! If you have any ideas about how you would change the syntax, I'd love to hear them.