The can opener puts a triangular hole in a can about an inch wide at the rim of the can. One would just move the churchkey over an inch and repeat. Each "levering" of the opener would open the can another inch. About the same as a P-38.
It doesn't leave a pretty lid and the inner lip of the can has the triangular cuts folded down on the inside but, in a pinch, it would work. The only time it would get messy is if you were opening a can of somewhat solid food like Corned beef hash.
They are usually used to open cans of liquid. The old oil cans, broth, tomato juice and others. a hole on one side and a vent hole on the opposite side of the lid.
Something like the SAK/Scout knife can opener would be much cleaner but for 19¢, the old churchkey is a classic that still works.