new

Creates a new anonymous module. If a block is given, it is passed the module object, and the block is evaluated in the context of this module using module_eval.

fred = Module.new do
  def meth1
    "hello"
  end
  def meth2
    "bye"
  end
end
a = "my string"
a.extend(fred)   #=> "my string"
a.meth1          #=> "hello"
a.meth2          #=> "bye"

Assign the module to a constant (name starting uppercase) if you want to treat it like a regular module.