Probably the Maybe monad most often, in usual code.

Or really as a shorter way of writing any smaller monadic code blocks.

I really look forward to using this new feature.

How? A sexy prime seems to be a pair of prime numbers, not one number.

2011 is, like 2017, a prime number. Therefore (2011, 2017) is a sexy prime, or a pair of prime numbers where one is larger than the other by 6.