These two constructs can be used with the following syntax:
if <expression> do # expression was truthyelse # expression was falsyendunless <expression> do # expression was falsyelse # expression was truthyend
As with the def construct, they can be inlined. For if, you'd do this:
if <expression>, do: # expression was truthy, else: # expression was falsy
For both constructs, the else clause is optional. They will return nil if the main clause doesn't match and no else clause was provided.