"Perez had another good game," manager Robin Ventura said. "He's tough in tight situations."
Whenever the White Sox did something positive over the weekend, the Royals were able to trump them.
Chicago didn't get its first hit against Royals starter Jeremy Guthrie until there were two outs in the seventh inning. They trailed 2-0 in the eighth when a two-run error by first baseman Eric Hosmer put Chicago in position to possibly steal the series finale.
But Kansas City quickly shrugged off the miscue and picked up Hosmer with a three-run rally in the eighth. Jesse Crain issued a leadoff walk to Billy Butler and speedy Jarrod Dyson came on as a pinch-runner. Dyson stole second on a close play and scored moments later when Perez came through with his RBI single to right.
The Royals added two insurance runs with the aid of an A.J. Pierzynski throwing error, and closer Greg Holland had a clean ninth inning to seal the sweep.
The White Sox (65-55) maintained a 1 1/2-game lead in the American League Central after the Tigers lost to Baltimore.
"Absolutely, it's disappointing," Pierzynski said. "We have to play better than that, myself included. Just a bad weekend. "
Trailing, 2-0, the White Sox had received a huge break in their half of the eighth. With two on and two outs, Kansas City manager Ned Yost went to Tim Collins for a lefty-versus-lefty matchup against Dewayne Wise.
Collins induced a grounder that went right through Hosmer's legs to let the tying runs score.
"When you catch a break like we did, that's a game you think you are going to win," first baseman Paul Konerko said. "You really want to win that one when you get kind of a gift like that to tie the game."
The White Sox didn't get their first hit off Guthrie until Konerko stroked a grounder into the shortstop hole in the seventh. Alcides Escobar made the pickup but threw low to first, and Hosmer couldn't make the clean catch with Konerko still far from the bag.
The official scorer ruled it a hit, and the Royals are planning to appeal that ruling even though Guthrie allowed two subsequent hits in the eighth.
"I just hit it and ran," Konerko said. "I'm not used to getting infield hits, but I'll take it."
Guthrie had a 22-innings scoreless streak going until the White Sox finally got on the scoreboard in the eighth.
"He had a lot of movement on his fastball," Konerko said. "Even when you are in fastball counts, there's still uncertainty on what the ball is doing. When you are cautious, you take bad swings or defensive swings."
The White Sox will try to regroup on a homestand that begins Monday with the Yankees coming to U.S. Cellular Field.
"It's over, and we have to get right back at them," Konerko said. "We can't think about this one or this weekend too much. It'll get worse if we do that. As hard as it is to cut this whole series loose, we have to do that and come in [Monday] with a smile on our faces and ready to rock."