relocated gas filler ???'s

I have a acura that I relocated the gas filler inside the trunk. I extended the 2 1/2" pipe but there was a smaller 1/2" line that connected to it and ran to the gas tank as well. Can anyone tell me what to do with this 1/2" line do I plug it or should I extend it too and reconnect it???????. what is this small tube for?????