Katy Perry has few regrets — including her decision to marry comedian Russell Brand. (And we know how that turned out.)

But the 28-year-old pop star, now dating singer-songwriter John Mayer, has named one thing from her past that she would like to take back: her 2011 sit-down with Barbara Walters.

"I shouldn't have done the interview," Perry told Billboard Magazine. "I was playing Madison Square Garden that same night, and I knew that the end of my marriage [to Brand] was coming. I was just exhausted and stressed," she explained.

[Related: Katy Perry After Russell Brand Divorce: "Should I Continue Living?"]

You see, Walters got testy with Perry when she arrived late to the interview.

"I'd prepped everyone that I was running late, but Barbara showed up at the original time anyway," Perry recalled, saying she apologized "immediately" to Walters when she finally appeared.

But Walters fired back. According to Perry, the 84-year-old broadcaster said, "I've only ever waited for one other person this long, and you know who that person was? Judy Garland. You know how she turned out, right?" (Garland struggled with substance abuse and accidentally overdosed on barbiturates in 1969 at the age of 47.)

Perry's reaction: "I was like, 'Oh, snap! Yes, b----!' I think it's the coolest thing that Barbara Walters shaded me."

And no, Perry's problem wasn't drugs and alcohol.

"I just couldn't tell her as we were sitting down for a mega-interview, 'Hey, my marriage is falling apart. Give me a break.'"

Watch Barbara Walters 2011 Fascinating People — Katy Perry Interview:

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