Tunisia equalized six minutes after the restart when Sliti set up Khazri on the right before the Rennes forward pulled the ball back to Ben Youssef, who stabbed a shot into the left corner.
Ben Youssef should have scored again two minutes later but sent a shot straight at Penedo when he had only the goalkeeper to beat.
Panama were under sustained attack and there was a sense of inevitability about the goal that put them behind in the 66th minute.
Oussama Haddadi began the move with a slide-rule pass from the left and Khazri was perfectly positioned at the far post to fire in his 14th international goal.
