methods.rb

module Foo
  def meth11
    # This will be an instance method
    11
  end

  define_method :meth12 do
    # This will be an instance method
    12
  end
end

Foo.instance_exec do
  def meth21
    # This will be a module method
    21
  end

  define_method :meth22 do
    # This will be an instance method
    22
  end
end

p Foo.instance_methods.include?(:meth11) # true
p Foo.instance_methods.include?(:meth12) # true
p Foo.instance_methods.include?(:meth21) # false
p Foo.instance_methods.include?(:meth22) # true