Perpignan, who survived a relegation playoff last season, upset Champions Cup holders Bordeaux-Begles 38–25 on Saturday in the opening match of round four of the French Top 14.
The Catalans, who won six league games last season, have two wins and two defeats – the same as UBB, who suffered their second away setback following their heavy loss at French champions Toulouse.
A week after suffering a 50-point thrashing at Montpellier, Perpignan showed clinical efficiency, scoring five tries, two while a man down.
"We made loads of mistakes, but what we'll take away from this is the players' spirit," Perpignan prop Enzo Forletta told Canal+.
"The aim in these big matches is to never give up until the very end. When you're up against the European champions, you need character – otherwise you can't achieve anything."
After giving the hosts the lead with a ninth minute try, winger Theo Forner earned an 18th minute yellow card for obstruction.
His team responded with a try. The first came from a lethal counter-attack finished off by centre Diego Mascarenc after 23 minutes. Hooker Sama Malolo then struck six minutes later from close range.
The visitors, who again rested star winger Louis Bielle-Biarrey and were also without injured fly half Mathieu Jalibert, were clumsy and sloppy.
They still hit back with tries either side of half time from No. 8 Tom Willis and centre Nicolas Depoortere.
Perpignan replied with a solo effort from scrum-half James Hall in the 53rd minute. Bordeaux, who had three potential tries ruled out, cut the gap to six points following a try by flanker Marko Gazotti in the 75th minute.
Tristan Tedder sealed victory with the hosts' fifth try on the final whistle. The full back converted his own try to finish with 16 points.
"We had possession and control throughout the match," said Bordeaux's Maxime Lucu.
"We had opportunities. The opposition scored three tries from three attacks – that's what decided the match. When we don't score, we get counter-attacked, and in the end that costs us dearly."