def embed_var(param)
      check_embed_envvar(param)
      erb = ERB.new(param)
      erb.result(binding)
    end
def embed_var(param)
      check_embed_envvar(param)
      erb = ERB.new(param)
      erb.result(binding)
    end
Embedding environment variable to parameter
 @param param [String] Embedding target command
 @return [String] Embedded command