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.
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.
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.
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.
