Compressed data isn't really usable -- that's the trade off you make for space.

If you can't temporarily decompress data, process it and then put it back, you have problems bigger than perl technique. You need more storage or a less wasteful record in the first place.

If you post more details or start a different thread, maybe we can get you fixed up in a whole other way. One that will get the answer you need at the end of the day w/o skinning this particular cat.