ObjectSpace.each_object(Module).select { |m| m.instance_method(:===).owner == m if m.method_defined? :=== }
=> [
  [ 0] Date < Object,
  [ 1] Gem::Platform < Object,
  [ 2] Proc < Object,
  [ 3] Range < Object,
  [ 4] Regexp < Object,
  [ 5] Bignum < Integer,
  [ 6] Float < Numeric,
  [ 7] Fixnum < Integer,
  [ 8] Symbol < Object,
  [ 9] String < Object,
  [10] Kernel,
  [11] Module < Object,
  [12] Gem::Requirement < Object
]