gistfile1.txt

$ ./bin/mirb 
mirb - Embeddable Interactive Ruby Shell

> Etcd::hoge
/Users/matsumotory/DEV/mruby/build/mrbgems/mruby-etcd/mrblib/etcd.rb:4: undefined method 'aaa' for Etcd (NoMethodError)
> 

gistfile2.txt

$ cat build/mrbgems/mruby-etcd/mrblib/etcd.rb 
module Etcd
  class << self
    def hoge
      aaa << 1
    end
    def endpoint
      @endpoint ||= "http://127.0.0.1:2379/v2"
    end

    def endpoint=(url)
      @endpoint = url
    end
  end
end

gistfile3.txt

MRuby::Build.new do |conf|
  # load specific toolchain settings

  # Gets set by the VS command prompts.
  if ENV['VisualStudioVersion'] || ENV['VSINSTALLDIR']
    toolchain :visualcpp
  else
    toolchain :gcc
  end

  enable_debug
  conf.gem :github => 'udzura/mruby-etcd'