gistfile1.rb

[1] pry(main)> class Foo
[1] pry(main)*   def hello
[1] pry(main)*     "Hello from Foo"
[1] pry(main)*   end  
[1] pry(main)* end  
=> nil
[2] pry(main)> module Mod
[2] pry(main)*   def hello
[2] pry(main)*     "Hello from Mod"
[2] pry(main)*   end  
[2] pry(main)* end  
=> nil
[3] pry(main)> f = Foo.new
=> #<Foo:0x000000016a7cb8>
[4] pry(main)> f.hello
=> "Hello from Foo"
[5] pry(main)> f.extend(Mod)
=> #<Foo:0x000000016a7cb8>
[6] pry(main)> f.hello
=> "Hello from Mod"
[7] pry(main)> b = Foo.new
=> #<Foo:0x00000001c9db40>
[8] pry(main)> f.hello
=> "Hello from Mod"
[9] pry(main)>