Torres opened the scoring in the 75th minute with a clever chip and set up Perez for the Panamanian's sixth goal of the competition.
Nacional played the last hour with 10 men after the ejection of defender Jose Pallas.
QUARTERFINALS, FIRST LEG:
Cucuta (Col.) 2 (Torres 75, Perez 90) Nacional (Uru.) 0.
Defensor Sporting (Uru.) vs. Gremio (Brazil) (Fox Soccer en Espanol, 6:30 pm ET)
Club America (Mex.) vs. Santos (Brazil) (Fox Soccer en Espanol, 8:30 pm ET)
Boca Juniors (Arg.) vs. Libertad (Para.) (Fox Soccer en Espanol, 8 pm ET)