Hi!
If you are travelling through this part of France I would not really reccomend visiting Perpignan, it's a slightly more industrial city, and you would need to go into some of the smaller areas to see the nice beaches (like St. Cyprien, which has a great beachside market) maybe 10-20km from Perpignan.
I would reccomend visiting Carcassone. It's a Medieval walled city and is beautiful. There are lots of places to stay around the actual site, but accomodations inside the "cité" can be quite costly.
To get back to Paris the train that runs from Toulouse to Paris is very quick.
Hope you enjoy your trip!
-Cassandra