What does Bill Murray list as his one regret in Zombieland?

Zombieland was one of those movies that really surprised me — it's pretty dang good.

And a big part of that was the unexpected cameo from comedy legend Bill Murray. Not only did he show up out of nowhere, he played himself ... well, himself dressed as a zombie in an attempt to fool the other zombies which instead gets him shot by humans.

While he's bleeding to death he mentions the one potential regret of his career. What was it?