Proc and ===

even = ->(x) { (x % 2) == 0 }

# we can use Proc#call
even.call(2)
even.call(3)

# also available to use ===, instead of using Proc#call
even === 2
even === 3

# we can use === in case statement as well.
fizzbuzz = ->(x) { (x % 3) == 0 && (x % 5) == 0 }
fizz = ->(x) { (x % 3) == 0 }
buzz = ->(x) { (x % 5) == 0 }

(1..100).each do |i|
  puts case i
  when fizzbuzz then "fizzbuzz"
  when buzz     then "buzz"
  when fizz     then "fizz"
  else i
  end
end

learned from RubyTapas#037 introducing more practical use case. it seems there must be a chance to use sometime :)