gistfile1.txt

class A
  
  def method
    puts 'do some stuff'
  end

  def method_with_same_name_as_in_module
    
  end
  
end

class B < A
  
  prepend :method
  def method
    puts 'do some stuff first'
  end
  
  prepend 'module-with-method.rb'
  
end

B.new.method
#=> do some stuff first
#=> do some stuff

gistfile2.txt