True that, but I struggled to find a better name to be short and self-explanatory. OTOH, I do not want to miss the opportunity to return what was indeed validated on success.

Maybe I should go with validate/1 to return what valid?/1 currently returns and valid?/1 to return boolean.

As I continue working on Exvalibur, I have implemented custom guards and pattern matching of values.

I just blogged about how I used custom sigils to allow quoted expressions in the rules.

For what it’s worth, here’s the convention about trailing question marks and boolean return values: https://hexdocs.pm/elixir/master/naming-conventions.html#trailing-question-mark-foo