Shouldn't be too hard. Off the top of my head:

1. Trap and record state info as the client code uses Net::FTP. Stuff you'll definitely need: login info, path changes.
2. Trap calls that could fail due a lost connection, which is probably just about all of them. Catch the error, then...
3. Reconnect and replay the stored state info to restart the transaction.

One obvious problem is that some things are not re-playable. You can't re-delete a file successfully, or re-create a directory. But for the common use-case of uploading/downloading a file it should work.

UPDATE: Haha, as webfiend pointed out the module already exists! In that case the answer is easier - you shouldn't implement it since it's already implemented! You should just use it.

-sam