made a mistake. You are actually not allowed to do so. My friend once tried this way. He was told he needed a new visa, since he already left Canada and came back.
For the time being, maybe you are fine. But who knows if you will have trouble in the future.
Back off a little bit, this way costs a little bit more than just simply to apply for a new visa. You need a multiple entry Canadian visas, which I believe it is $150. You need extra money to travel to and from Canada, plus hotel and food.