"I am woman, hear me roar." It's the simple phrase that Helen Reddy sang in 1971, encouraging women all over America to burn their bras as part of the liberation movement. And 42 years later, the same words inspired Katy Perry to write her own empowerment theme, "Roar."

In an interview with Radio.com, Perry's co-writer on the track, Bonnie McKee, said writing "Roar" was a turning point for Perry, who at the time was still coping with her 2011 divorce from Russell Brand.

"She was kind of coming out of sort of a dark place when she was setting up Prism," McKee said. "She was talking about wanting to explore her darker side."

McKee, who previously worked with Perry on Teenage Dream hits "California Girls," "Last Friday Night (T.G.I.F.)" its title track, was willing to go to the dark side with her longtime pal. McKee's skill as a songwriter lies in the fact that whatever artists she's working with, whether it's Ke$ha or Britney Spears or Kelly Clarkson, her goal is to make the song fit said performer's personality.

"I have my songwriters' hat on," McKee said in regards to when she works with other artists. "I'm asking them what they're going through, what they want to talk about, who they want to be."

To help Perry get comfortable, the two headed back to the singer's hometown of Santa Barbara, California to work on the album. As McKee explained, the song ended up being a cathartic experience for Perry. "Prism went from being a dark album, to being an empowering album full of light," she said.