Fuel overflow problem

Usually only add fuel when I check with my fuel indicator tube and it is at or below 3 gallons indicated.   After today's flight I figured I could add 5 gallons to each tank.  The Rt tank took five gallons and the left about 4.5 AND before I stopped it started to overflow!   I put the cap back on and taxied back to my hangar.  After putting the plane the hangar I was putting in a new push-to-talk.  Suddenly, I noticed fuel dripping below the fuel sight gage for the left tank!  Got out of the plane and looked underneath and fuel was dripping on the bottom.  Pulled the plane out of the hangar and took the cap off and fuel came out over the wing.  I opened the fuel sump valve and left it open for about ten minutes or so. The fuel coming out of the sump was slower than what I am used to in Bonanzas.  A stream but not very fast.  So, what happened other than the obvious, overfilling?   Is there a fuel overflow valve or something for the main tanks.  I felt down where the sight glass is for the left tank and seemed there was an opening or hole where fuel could escape.  

Any way, after moving the wing a little and getting the fuel below the top the leaking stopped.