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.
We all know someone who pretends to have very quiet, respectable tastes until the weekend hits. In "Se Vuelve Loca," the Latin pop boyband CNCO calls out a girl playing completely innocent. At home, she claims she only listens to romantic ballads and Ricardo Arjona: "Dice que le gusta Arjona y baladas por montón" (She says she likes Arjona and a ton of ballads), looking like an absolute saint ("una santa, cómo no"). Arjona is a famous Guatemalan singer-songwriter famous for poetic, dramatic love songs, so using his name here is a funny way to describe someone acting super serious and wholesome.
The act falls apart the second the club lights go down. As soon as the beat drops, her true self takes over: "Pero cuando está en la disco y le ponen reggaetón / Ella se vuelve loca" (But when she is at the club and they play reggaetón / She goes crazy). CNCO hypes her up to stop pretending and dance freely, shouting "saca la fiera que llevas dentro" (bring out the beast inside you). They also bring in classic party slang with "el vacilón" (the party / fun times) and tease that she secretly loves being the center of attention on the dance floor. It is pure, infectious party energy about dropping the polite mask and letting loose.