const.rb

original_object_constants = Object.constants

O = "on Object"

class StaticClass
  A = "on StaticClass"
end

DynamicClass = Class.new do # or Module.new
  B = "on Object"
  self::C = "on this class"
end

StaticClass::D = "on StaticClass"
StaticClass.class_eval { E = "on Object" } # or class_exec
StaticClass.class_eval 'F = "on StaticClass"'

puts "Constants of StaticClass:  #{StaticClass.constants}"
puts "Constants of DynamicClass: #{DynamicClass.constants}"
puts "Constants of Object:       #{Object.constants - original_object_constants}"

# constant resolution

class Parent
  def const
    # CONST # uninitialized constant Parent::CONST (NameError)
    self.class::CONST
  end
end

class Child < Parent
  CONST = :const
end

Child.new.const

# class/module definition

C1 = Class.new do
  module M # toplevel
  end
end
p M

C2 = Class.new do
  module self::M # in this class
  end
end
p C2::M # => #<Class:0x00000100ad6550>::M

output.txt

Constants of StaticClass:  [:A, :D, :F]
Constants of DynamicClass: [:C]
Constants of Object:       [:O, :StaticClass, :B, :DynamicClass, :E]
M
#<Class:0x0000010108b658>::M