1. Multi-word lines without leading parens are grouped with later indented lines.
2. Indentation is not sensitive inside parens.
More info, unpacking the implications: https://github.com/akkartik/wart/blob/47e3572a29/004optional...
Infix works by using a disjoint set of 'operator characters' that isn't available to prefix symbols. More info: https://github.com/akkartik/wart/blob/47e3572a29/006infix