Luke Berry and a double from Elijah Adebayo had Luton in control at the break, but Jamie Paterson and Olivier Ntcham hit back before Piroe snatched a point at the death.
The hosts made a rip-roaring start to the game when, with only seven minutes gone, Harry Cornick's long throw was headed up in the air for midfielder Berry to unleash a superb acrobatic scissor kick volley which flew past Ben Hamer and into the net.
Striker Adebayo then slammed over from outside the box before Town had a penalty on 15 minutes, Cornick robbing Kyle Naughton who brought him down for a spot-kick that Adebayo thumped beyond Hamer.
Luton had a third on 23 minutes though when a magnificent team move saw Kal Naismith's crossfield ball fall perfectly for James Bree, who controlled on the run and picked out Adebayo at the back post to add his second.
Naismith headed over from a Henri Lansbury corner, while Adebayo could have had a hat-trick, racing on to a clearance from Gabe Osho, but prodding wide with just Hamer to beat.
The visitors had a great chance to pull one back in first half stoppage-time, Ethan Laird doing well on the right hand side before crossing for Paterson to send his volley wide from a few yards out.
Swans boss Russell Martin made a triple substitute at half time, bringing on top-scorer Piroe, before Michael Obafemi rifled narrowly over and then Paterson hit the top of the bar from 20 yards.
The Hatters continued to press too, Bree shanking wide when meeting fellow full back Osho's cross, before Cornick should have had a fourth as he was teed up by Adebayo with just Hamer to beat but he side-footed against the inside of the post.
Swansea made Luton pay straight away, Paterson unleashing an effort from outside the box on 66 minutes which deflected off Naismith and beat Simon Sluga.
Naismith then sent a free kick over the top, while Piroe's volley was narrowly off target after escaping the Luton defence.
The visitors pulled another back with five minutes to go when Ntcham's 25-yard strike deflected off Pelly-Ruddock Mpanzu and beat the motionless Sluga.
Swansea then drew level in stoppage time, Piroe clinically finding the bottom corner.
They might have even won it at the death but Obafemi was denied by a posse of Luton defenders.