Brighton won a corner, March had the ball at the flag and was ready to take it quick. Perisic was coming back on the field, saw Spurs weren't ready, and grabbed a ball and rolled it onto the pitch - not even towards the corner flag, literally just so there were two balls on the pitch as March...
Perisic grabbing a 2nd ball and throwing it on the pitch to stop a quick Brighton corner too. Probably not against any rules but just another example of how officials let them get away with things without even having a word with them.