Perlis food is comprised of mainly typical Malay dishes but with a hint of Thai influence -- a more liberal use of chillies and fresh herbs, for instance. In the evenings finding food can be tough around Kangar's town centre as nightlife is practically non-existent -- there are no bars or clubs in this Muslim town. But during the day plenty of lunch places and roadside food stalls are open, usually from very early morning for local style breakfast until around 16:00-17:00.
Right next to Pasar Raya are a couple of roadside stalls and right behind the supermarket building is a good Malay lunch spot that does nasi kandar buffet and fried rice dishes starting at 4 ringgit for a meal.
Along Jalan Kangar going out of town next to the fire station is a small Malay breakfast joint doing cheap curries and breads, and towards the intersection are a couple of seedy looking Chinese joints open 17:00-22:00 that sell beer.
At night opposite the express bus station, next to the big Chinese temple, is a cluster of Malay food places and cafes with outdoor seating areas and plastic chairs that do quick fried rice dishes, noodles, local style chicken with coleslaw, and so on. If you are waiting for the bus, then here is the place to eat. The Kangar food scene may have some great and tasty local dishes, but finding a spot open when you need to eat can be an adventure itself.
KFC in the main square, just a few steps out of Hotel Ban Cheong, is open 24/7 so it's always a last resort.