| self.keyword_p("ls")
>> ! path
>> eps_p [ bind(&PD::builtin_ls)(d_, path_) ]
+ | self.keyword_p("lr")
+ >> ! path
+ >> eps_p [ bind(&PD::builtin_lr)(d_, path_) ]
| self.keyword_p("exit") [ bind(&PD::builtin_exit)(d_) ]
| self.keyword_p("help")
>> ! path