DONT'T fool around with this! Have the copper line replaced immeadiately! Shut off the gas valve on the tank until the repair can be made. Call the people that fill your tank, and have then arrange the repair or recommend a plumber.
Propane is heavier than air, can seep into the ground, find its way into your house and, cause a fire/explosion. This exact thing happened to a family about 60 miles from where I live and it killed several people in the family.
DO IT NOW!