For those confused, Pearl is an entirely different character from Barry.

Pearl is arguably the head Commando of the Sinno Dex Holders. He's very quickwitted and takes charge. Dia is his childhood as the two are always together practicing their comedy sketches. Pearl even taught Platina how to battle before becoming good friends with her.

Pearl has a unique ability from watching many Pokebattles his father took in. He's able to perfectly predict a Pokemon's next move before they can even perform it just from the Pokemon's stance. This makes him a dangerous opponent.