gistfile1.txt

irb(main):001:0> class A
irb(main):002:1>   def foo
irb(main):003:2>     puts "class A's foo is a bar"
irb(main):004:2>     end
irb(main):005:1>   end
=> nil
irb(main):006:0> module B
irb(main):007:1>   def foo
irb(main):008:2>     puts "mod B's foo is a baz"
irb(main):009:2>     end
irb(main):010:1>   end
=> nil
irb(main):011:0> a = A.new
=> #<A:0x11ae9a0>
irb(main):012:0> a.extend B
=> #<A:0x11ae9a0>
irb(main):013:0> a.foo 
mod B's foo is a baz
=> nil