Two judges scored the fight 114-113, one in favor of Perez and the other for Jennings, while the third deemed Jennings a 115-112 winner. A one-point penalty to Perez for hitting after a break in the final round, in effect, sealed the win for "By-By."
For his mandatory title shot at the World Boxing Council belt, which likely won't come until the spring, Jennings (19-0, 10 knockouts) will fight current WBC champion Bermane Stiverne (24-1-1, 21 KOs) or knockout artist Deontay Wilder (31-0, 31 KOs). Stiverne, a 35-year-old from Haiti, and Wilder, a 6-7, 28-year-old from Alabama, are expected to battle in November or December.
"Whoever the guy is, [Jennings is] 19-0 and he's got a proven record of adjusting to the situation and pulling off the win," said Jenkins, Jennings' trainer. "So I don't think it'll be different with either one of them."
Perez made for arguably Jennings' toughest pro fight yet. It wasn't the most aesthetically pleasing. Jennings lamented his opponent's lack of willingness to trade punches. Jenkins said he was surprised by how much Perez (20-1-1, 12 KOs) held Jennings - "He must've had a nickname, Perez the Holder," Jenkins quipped - which led to Jennings throwing more body shots. He landed 29 percent of his 513 punches while Perez connected on 20 percent of his 571.
Perez, a slick, 28-year-old southpaw with almost 20 pounds on the cut, 225-pound Jennings, controlled the fight's early rounds. Jennings landed a combination in the fifth round, a clean left hook in the seventh and an uppercut in the 11th. Judge Joe Pasquale ruled Jennings the winner of each of the last six rounds. Tom Schreck had Perez claiming the final two.
Jennings insisted he did not study film of Perez, a Cuban defector with vast amateur experience. The only time Jennings had seen him fight was in person on Nov. 2 against Magomed Abdusalamov at Madison Square Garden. Jennings, who prides himself on his ability to make midfight adjustments, said it's the way he always prepares for fights, but added he might start watching film to help produce better starts.
Given he's only about 4 1/2 years into his pro career, the progression will continue for Jennings. The former standout defensive end at Ben Franklin High often catches himself thinking about the implausibility of it all.
"I think about that all the time, like even when I attend fights," said Jennings, who drew a vocal Philly crowd to the "Mecca of Boxing."
"I look at it like, 'I really do this. I get in there.' It's just like, 'Wow.' It's crazy."
The boxer's experience spans only 5 1/2 years, but Jenkins starts the story 7 years ago. That's when the trainer says he began badgering the well-built young man on the basketball courts at North Philly's ABC Recreation Center.
"I saw his talent before he even knew he had talent," Jenkins said. "He's a good listener . . . he's got plenty of heart and he's willing to take some gambles. That's what makes a good fighter.
"Every time I saw him, I always asked him, 'When you gonna come in and try the gym? When you gonna come in and try the gym?' He said, 'I don't know, man, I'll be in there.' He pushed me off for 2 years and then January  he walked in and said, 'I'm gonna try.' "
Said Jennings: "It was just timing. I don't know what really took me so long. I wasn't really feeling it. And then it was like, 'Let me see what's up with this.' I came in and immediately, 'Boom.' "
Now look at him, one win away from becoming Philadelphia's first heavyweight champ since "Terrible" Tim Witherspoon wore the WBA belt in 1986 and only the second since the legendary Smokin' Joe Frazier.
"Now," Jenkins said, "we've got the No. 1 kid in the world."
On Twitter: @jakemkaplan