阅读下面的诗歌，回答相关问题。
                                                                               酬乐天扬州初逢席上见赠
                                                                                            刘禹锡  
                                                                         巴山楚水凄凉地，二十三年弃置身。
                                                                         怀旧空吟闻笛赋，到乡翻似烂柯人。
                                                                         沉舟侧畔千帆过，病树前头万木春。
                                                                         今日听君歌一曲，暂凭杯酒长精神。