Toulouse coach Guy Novès was disappointed he could not celebrate his 1,000th match with the French champions with a victory.
South African centre Gavin Hume scored the only try as Perpignan defeated Toulouse 19-18 in Friday's Top 14 hit-out.
Hume scored with 10 minutes left with Welsh fly-half James Hook kicking the crucial extras as Perpignan came back from 18-12 down to condemn Toulouse to a first loss at their Stade Ernest-Wallon home in almost three years.
Former All Black Luke McAlister kicked all of Toulouse's points with Hook equally accurate as the defending champions - stripped of seven international players away on Six Nations duty - slumped to a second successive domestic defeat.
"It's a bitter defeat because I feel we dominated the match until the last 10 minutes," said manager Noves, who insisted he would trade the 1,000-match mark for a win.
"I'd prefer to have 100 fewer matches and have won tonight."
Novès has been associated with Toulouse since 1975 when he made his debut as a player before progressing to coach and manager.
The 59-year-old, who has led the club to a record four Heineken Cups and been involved in 10 national titles, even turned down the opportunity to take the reins of the French national team in 2011 to remain loyal to his long-time employers.
After his 259-game playing career ended in 1988, he had overseen 740 matches as coach and manager - including 540 in the Top 14 and a record 131 in the Heineken Cup - up until Friday.