class Moi
[1] pry(main)*   def []=(key,value)
[1] pry(main)*     p key, value
[1] pry(main)*   end
[1] pry(main)* end
=> :[]=
[2] pry(main)> Moi.new["foo"] = "bar"
"foo"
"bar"
=> "bar"
[3] pry(main)>