gistfile1.txt

class Person
  def say_hello
    "Hello"
  end
end

class Person
  def say_goodbye
    "goodbye"
  end
end

p = Person.new
puts p.say_hello
puts p.say_goodbye

class Person
  def say_goodnight
    "goodnight"
  end
end

puts p.say_goodnight


p2 = Person.new

class << p2
  def say_hello
    "Hi there!"
  end
end

puts p2.say_hello
puts p.say_hello

p3 = Person.new
def p3.say_hello
  "Hola!"
end

puts p3.say_hello
puts p2.say_hello
puts p.say_hello