I have to say, my first (and rather uncharitable) thought when I saw this was, "Does the world really need another templating language?" I've been really happy with Haml for years now, and have reached moderate levels of satisfaction with Jade when I can't use Haml.
Also, it wasn't clear to me from looking at https://gitlab.com/Polly-lang/Polly/blob/master/GUIDE.md#var... how I would actually write, say, an email addressing including an "@" symbol (I'm sure it's possible, just not documented there).