The acquisition of German Mustafi and Deportivo speedster Perez for a respective £35m and £17m took the Gunners' summer outlay on new players to £96.1m — a new record for the club.
After spending £30m on Granit Xhaka in May, Arsenal's purse-strings pullers fielded growing calls from fans to dip into the club's considerable cash reserves and make new additions to the squad.
Yet, after a relatively quiet June and July, when youngsters Rob Holding and Takuma Asano joined for a combined £6m, Arsenal have taken their spending to a level never before seen in a single window at the Emirates.
The club's previous record outlay came two years ago when £89.5m was spent on Alexis Sanchez, Calum Chambers, Danny Welbeck, Mathieu Debuchy and David Ospina.
At £35m, Mustafi is the most expensive defender ever signed by Arsene Wenger, who has also never spent more on a centre forward than the £17m exchanged for Perez.
It means that with just 11 hours remaining in the summer transfer window, only Manchester United and Manchester City, who have forked out £157.2m and £180.9m respectively, have spent more this summer than Arsenal.
Yet despite hitting a new club record for transfer spend in a single window, Arsenal's £96.1m window has been topped 13 times before by United, City, Chelsea, Liverpool and arch-rivals Tottenham.