# What's it look like?
set = { 1, 2, 3 }
set.include?(3) # => true

# Originally this might have looked like this:
set = Set[1, 2, 3]
set.include?(3) # => true

Source: Ruby 3 - Set Literal - DEV

To be honest, Set[1, 2, 3] seems fine to me vs new syntax. Really, I just need to remember it’s there when I don’t care about order.