He definitely bottled the second yellow for De Bruyne and once he had done that he really had no choice but, to let Perez' second one go as well. In that respect both teams were lucky and probably should have been down to 10 players each.
Makes me feel sick when they can remove a player like De Bruyne and replace him with Bernardo Silva.... meanwhile we have Callum Roberts and Jacob Murphy trotting up and down the line warming up... (nowt wrong with either player but, a hell of a gulf in ability compared to their bench options).
Had the ref done his job De Bruyne would not have been on the pitch for Perez to foul