The only flights into Perpignan seem to be with Air France (from Paris Orly), Ryanair (from London Stansted), FlyBe (from Southampton) or BmiBaby (from Manchester).
There don't appear to be any direct flights to Paris (either Orly or CDG) from Capetown. Flying into London would mean transferring from either Gatwick or Heathrow to Stansted (which is a bit of a pain). There are no direct flights from Cape Town to Southampton and the only operator between Cape Town and Manchester (Fly GlobeSpan) doesn't fly that route until November. So, any route entirely by air would have to involve a complicated 'multi-hop' journey.
Your best route might be to take an internal budget flight to Jo'burg. (Approx ZAR500 return, including taxes, with Kulula). Then fly to Barcelona with Iberia. (ZAR8,100 return, including taxes, for the dates I checked). Take the train (RENFE Line 10) to Barcelona Sants station.(about ZAR50 return), then use the train along the coast to Perpignan (about ZAR325 return if you take the local services, with one change, or ZAR650 return if you use the direct international trains).
Chris