Within the song's lyrics, Cash reflects upon his life, wondering about what he should have done, and if he made the right decisions throughout his life. Through the lyrics "The needle tears a hole, The old familiar sting, Try to kill it all away, But I remember everything" means that he realizes what he has done, and no matter how much he tries to forge, he knows that the regret will always be there. Just as with Cash, Barth can never forget how shallow and uncaring he was, and it will burn a hole in him, and all his clones, for the rest of their lives.
A second set of lyrics that I think really connects with the story is the set " Beneath the stains of time,the feelings disappear, you are someone else, I am still right here." This set of lyrics means that though life has continued to go on, he has stayed the same man, and not a good one. The people that he love have moved on with their lives, and Cash regrets that he didn't move along with them. This relates because the only thing that Barth seems to love int the story, other than himself, is a girl named Lynette. But by the end of the story, he regrets what he keeps doing to her, and that he keeps her back as she tries to move on with her life.

"Hurt" - Johnny Cash
Bibliography:
Cash, Johnny. "Hurt." American IV: The Man Comes Around. Universal Music, 2003. CD.*
Author N/A. Regret. Muncie Voice, 2012. 2012.
*This is the citing of the formal album of the song, not the web page upon which it was linked.