SIRIKI DEMBELE struck a hat-trick, won a spot-kick and was on the receiving end of a red-card challenge.
He was fouled for the penalty from which Jonson Clarke-Harris gave Peterborough the lead and restored the advantage after Josh Daniels had equalised.
Josh Vela was dismissed for a foul on Dembele, who struck twice in the second half before Jack Taylor added a fifth. Manager Darren Ferguson said: “Siriki was absolutely brilliant. We all know what he is capable of doing and today everyone saw it.
“The challenge on him for the red card was nothing short of a disgrace, but he picked himself up, got on with it and got himself two more goals in the second half.”
Shrewsbury boss Sam Ricketts said: “Ultimately individual errors cost us.”