阅读下面这首诗，然后回答问题。
                                                            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。