prelude: |
  small_ary1 = [1, :a, nil, 2]
  small_ary2 = [1, :a, nil, 2]
  large_ary1 = Array.new(1000) { |i| i }
  large_ary2 = Array.new(1000) { |i| i }
  str_ary1 = Array.new(100) { |i| i.to_s }
  str_ary2 = Array.new(100) { |i| i.to_s }

benchmark:
  small_ary.eql?: small_ary1.eql?(small_ary2)
  large_ary.==: large_ary1 == large_ary2
  large_ary.eql?: large_ary1.eql?(large_ary2)
  str_ary.eql?: str_ary1.eql?(str_ary2)