Northampton (20) 23
Tries: Foden, Clarke Cons: Myler 2 Pens: Myler 3
Perpignan (7) 7
Try: Guirado Con: Porical
Clarke's solo try meant Northampton were virtually home by half-time
A dominant first-half display from Northampton helped them rip Perpignan apart and set up a Heineken Cup final against Leinster.
Ben Foden cruised over early on before Jon Clarke scored a fine try, with Stephen Myler converting both and adding two penalties to make it 20-0.
Guilhem Guirado scored a converted Perpignan try just before half-time.
But Myler added a third penalty as Saints trained their sights on the final in Cardiff on 21 May.
Northampton are bidding to become the first team to win every match in the pool stages and then go on and win the entire tournament.
But the Saints will surely face a tougher test against 2009 winners Leinster at the Millennium Stadium than that posed by Perpignan.
The Catalan club pride themselves on the power of their scrum but when Northampton matched and then bested them in that area their heads dropped and their increasingly poor discipline enabled the English side to wrap the game up by half-time.
Northampton also looked far more threatening out wide, with England full-back Foden a constant threat on the counter, and they will head to Wales with every hope of adding a second Heineken Cup to the title they won in 2000.
Perpignan fly-half Nicolas Laharrague missed a long range drop-goal and Myler was off target with a penalty from near the left touchline before Saints took the lead with a cracking try.
Phil Dowson burst through the midfield from James Downey's pass and although the flanker was tackled by Perpignan full-back Jerome Porical, Saints recycled quickly and Foden cruised over unopposed.
This time Myler found the target with his kick and Northampton immediately threatened again as Foden launched a sizzling counter-attack, but Perpignan managed to scramble back and snuff out the threat.
Northampton did not need any help but they were given some when referee George Clancy incorrectly penalised David Marty for offside when he collected a gem of a chip from Laharrague, and Myler drilled over the resulting penalty from halfway.
The fly-half soon missed a penalty from a similar range but Northampton were well on top and extended their lead as Perpignan's midfield defence again parted like the Red Sea.
The English side were held up as they tried to drive over from a short-range line-out but when they moved the ball wide, Clarke stepped off his left foot and cruised over untouched from outside the 22 for a converted try.
Candelon was yellow carded after taking out Dickson in the air
Julien Candelon was then yellow-carded for taking out Saints scrum-half Lee Dickson as he soared to take the restart as Perpignan's increasingly shaky discipline completely deserted them.
The scrum-half landed on his shoulder and head and was fortunate not to suffer serious injury.
And three minutes before the break Myler landed his second penalty to make it 20-0 to Northampton.
Perpignan desperately needed something before half-time to keep alive their hopes of a trip to the Millennium Stadium and they got it in the dying seconds of the half as Guirado finished off a drive from a line-out.
Laharrague made it 20-7 with the conversion but Northampton, who had seen captain Dylan Hartley bundled into touch inches from the line soon after the restart, extended their lead through Myler's third penalty eight minutes into the second period.
Perpignan's sole attacking tactic seemed to be to try and bully their way over from close-range line-outs, but Northampton were in no mood to ship any more tries in that manner and they repelled a series of attempts from the French team after the break.
As the game moved into the final 15 minutes Northampton confirmed they had broken the Perpignan spirit when they destroyed their much-vaunted scrum with a massive drive.
The Saints ended the game on the attack and although they could not add to their lead they were worthy winners after a powerful performance which will have given Leinster plenty to think about over the next three weeks.
Northampton: Foden; Ashton, Clarke, Downey, Diggin; Myler, Dickson; Tonga'uiha, Hartley, Mujati, Lawes, Day, Dowson, Clark, Wilson.
Replacements: Ansbro for Clarke (76), Commins for Dickson (79), Waller for Tonga'uiha (79), Sharman for Hartley (79), Mercey for Mujati (76), Sorenson for Day (73), Easter for Clark (79).
Not Used: Geraghty.
Perpignan: Porical; Plante, Marty, Hume, Candelon; Laharrague, Mele; Freshwater, Guirado, Mas, Alvarez, Tchale-Watchou, Le Corvec, Guiry, Chouly.
Replacements: Michel for Porical (70), Edmonds for Laharrague (72), Boulogne for Mele (72), Schuster for Freshwater (60), Geli for Guirado (73), Pulu for Mas (73), Vilaceca for Alvarez (67), Tuilagi for Le Corvec (50).
Sin Bin: Candelon (31).
Ref: George Clancey (RFU).