#  A module may contain constants, methods and classes.
#  No instances

module Stuff
  C = 10
  def Stuff.m(x)  # prefix with the module name for a class method
    C*x
  end
  def p(x)        # an instance method, mixin for other classes
    C + x
  end
  class T
    def t
      @t = 2
    end
  end  
end
puts Stuff::C     # Stuff namespace
puts Stuff.m(3)   # like a class method
x = Stuff::T.new
puts C            # uninitialized constant error