Sean Lamont suffers a double tackle against Perpignan
The Scarlets' slim hopes of qualifying for the Heineken Cup knock-out stages evaporated in the south of France as Perpignan sealed a bonus-point victory.
Perpignan, who secured a home quarter-final, opened up a 22-0 lead in the first half with three tries for Jerome Porical, Henry Tuilagi and Farid Sid.
The Scarlets did score early in the second half with a Jonathan Davies try but it was too little, too late.
To make matters worse, Scarlets prop Simon Gardiner was stretchered off.
It is another crucial injury blow with the Welsh region already without fellow tight-heads Deacon Manu and Peter Edwards (broken arms).
In bright sunshine it took the French side only four minutes to get on the scoreboard.
The Scarlets did not help themselves by losing their own line-out ball. Possession was spread left along the back-line until full-back Porical collected his own chip ahead to score.
The Scarlets, who had hoped to silence the crowd early on, were stunned by the early try and then gave a penalty away after the Perpignan pack mauled them 40m up-field, but Porical was wayward with his kick.
The miss mattered little though as the home side went over for a second try only two minutes later. Morgan Stoddart was caught in possession in his own 22 and Perpignan moved the ball quickly as number eight Tuilagi went over.
The Scarlets' error-strewn start did not improve as they were caught offside in front their own posts, but they had a let-off as Porical was off target again.
Some rare attacking ball for the Scarlets saw Gareth Maule kick ahead to the Perpignan 22 before the French got back in numbers.
Stephen Jones missed a 17th-minute penalty, but the Scarlets went through some impressive phases only to lose possession.
They earned them a second penalty but Rhys Priestland was well short from near halfway.
The Scarlets were given a lesson in clinical finishing as lively scrum-half Florian Cazenave put wing Sid over on 32 minutes to concede the third try.
Just before half-time the visitors did win a line-out close to the Perpignan line but in going for a driving maul they lost possession.
The Scarlets started brightly after the break and were rewarded with a try for Davies after good work from Priestland and Maule.
But that score was soon cancelled out as centre Maxime Mermoz broke through to send Cazenave over for the bonus-point try, although referee Dave Pearson had to go to the television match official to confirm the conversion had gone over.
Laharrague added a penalty before the Scarlets suffered the injury to Gardiner.
There was more bad news for the Scarlets as they conceded a fifth try as replacement Gerrie Blitz went over after another impressive rolling maul.
Defeat for the Scarlets meant there will be no Welsh region in the Heineken Cup last eight for the first time in four years.
Perpignan: Porical, Sid, Marty, Mermoz, Candelon, Laharrague, Cazenave, Freshwater, Guirado, Mas, Olibeau, Vilaceca, Chouly, Guiry, Tuilagi. Replacements: Michel for Porical (59), Mele for Cazenave (56), Pulu for Freshwater (59), Tincu for Guirado (56), Bourrust for Mas (59), Tchale-Watchou for Vilaceca (59), Britz for Tuilagi (50). Not Used: Tonita.
Scarlets: Priestland, Stoddart, Maule, J. Davies, Lamont, S. Jones, Knoyle, I. Thomas, M. Rees, Gardner, Reed, Fa'amatuainu, McCusker, Turnbull, Lyons. Replacements: L. Williams for Priestland (71), Roberts for Knoyle (57), R. Jones for I. Thomas (71), Phillips for M. Rees (68), John for Gardner (57), Welch for Fa'amatuainu (50), Pugh for McCusker (57), Morgan for Lyons (56).
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