Independiente pegged back by Gimnasia
Perez scored midway through each half to help Gimnasia to a 2-1 victory over Independiente, whose midfielder Federico Mancuello hit an equaliser five minutes before halftime.
Independiente, who had been unbeaten in seven matches, have 27 points from 13 games, three points ahead of second-placed Godoy Cruz who visit Racing Club on Thursday.
Title holders Banfield beat San Lorenzo 2-0 to hand their new coach Sebastian Mendez, appointed after Diego Simeone resigned at the weekend, a losing start.
It was the eighth defeat in 13 games for San Lorenzo, one of several ailing giants of the Argentine game including Boca Juniors, River Plate and Racing Club.
Midfielder Roberto Battion put Banfield ahead after 12 minutes, heading home Walter Erviti's corner, and striker Ruben Ramirez converted a penalty two minutes before halftime.
Banfield are joint third with Argentinos Juniors, away to Rosario Central on Thursday, on 22 points.
Struggling giants River Plate lost 1-0 at home to Newell's Old Boys who scored from a lucky rebound six minutes into the second half through Paraguayan Jorge Achucarro, who was falling over as he lobbed keeper Daniel Vega.
River have lost their last four matches without scoring. They have the third worst attack in the division with eight goals in 13 games.
Former Argentine forward Ariel Ortega was brought back into the team by coach Leo Astrada after a long absence due to the veteran player's drinking problems and he was one of the better players on the pitch.
However, the River faithful in the stands were baying for the players' blood as they walked off heads bowed at the end, some palming their hearts demanding the players show more passion and fight.
Tigre striker Carlos Luna scored twice in their 3-1 win over bottom team Atletico Tucuman on Tuesday to join Mauro Boselli of Estudiantes at the top of the scoring chart with nine. Gimnasia's Perez is next with seven.