class MyClass
  class<<self
    def new(*args)
      ret = if (args.size == 1 && args[0].kind_of?(String))
        obj = allocate
        obj.send(:initialize,*args)
        obj
      else
        false
      end
    end
  end
  def initialize string
    @my_name = string
  end
end

puts MyClass.new(123).inspect          # => false
puts MyClass.new("hello").inspect     # => #<MyClass:0x101071ed8 @my_name="hello">