Sounds like one of the steel lines inside the tank has a rust hole in it. This happens from time to time.
Is the fuel running out of a black rubber hose down by the side stand?
The fuel tank vent line, and the overfill line, both travel from the filler cap area via steel tubes inside the tank, down to the hose barbs on the back of the tank under the seat. The hoses then run down to the bottom of the bike. The one on the left is the tank vent, and the one on the right is the overfill line (on Non-CA models).
If either one of these steel tubes rust through, and they will, they'll leak fuel out on the ground.
Rem