What I had for lunch

My bank account was low, so I took a walk to the end of the rainbow, hoping to grab a few handfuls from the pot of gold.

The pot was filled with cans of tuna fish. I like tuna fish. But I can’t pay bills with them.

I asked the rainbow if it could fill its pot with currency. The rainbow said it could only refill the pot when it was empty.

I sighed and asked if it had a can opener?