Berber is a carpet of contiguous 'thread'. Once it gets a pull, it can be disasterous!
The berber may be able to be grafted. Contact a professional to have it done. If it's not done right, it can be made worst. Pets and even high heels are 'bad' for berber carpet. Pulls in this carpet are its greatest downfall.
You may be able to 'seal' it up with some glue and have it reinstalled under a couch or along another wall, or something. Other than that, you may be out of luck. Next time there is a pull, cover it with something until you get it repaired. (I wouldn't suggest you pull out the berber thread as it's used in the repair. The pro may be able to use other threads if either you have 'remnants' or a hidden edge that can 'afford' to have some thread removed. He'll seal that up too.)