Perrea comes from perreo, a style of dancing closely associated with reggaetón music. It literally translates to 'she twerks' or 'she dances' in that specific sensual, grinding style.
In this song, CNCO contrasts the woman's seemingly innocent image at home ("una santa") with her behavior at the club, singing "Le encanta que la vean cuando ella perrea" (She loves it when they watch her when she twerks). This word is a culturally rich term that captures the infectious energy of Latin urban music and is key to understanding the song's playful celebration of letting loose on the dance floor.
Have you ever known someone who acts one way but is completely different when they let loose? That's exactly what CNCO is singing about in "Se Vuelve Loca"! The song is all about a girl who pretends to be quiet and reserved. She says she likes ballads, specifically mentioning the singer Arjona: "Dice que le gusta Arjona y baladas por montón" (She says she likes Arjona and tons of ballads). But the guys from CNCO see right through her act.
They know that as soon as she's in the club and a reggaeton song comes on, her secret personality comes out. She goes from a supposed saint, "una santa, cómo no" (a saint, of course), to the life of the party. She loves being the center of attention while she dances, and the singers encourage her to embrace it, telling her to "saca la fiera que llevas dentro" (bring out the beast you have inside). It's a fun track about letting go of your inhibitions and just enjoying the music you secretly love.