after a dbi subroutine call any system call as example given above returning the message "no child process for $? & $! conatins "-1" as status.

So? It makes no sense to check $! unconditionally. As documented, $! is meaningless except after a system call that resulted in an error. You haven't been told there was an error by a system call. You haven't even made any system calls.

As for $?, if you want gzip's status, you should save $?'s value closer to the backticks.

Sorry, but $! and $? changing is not a bug.

By the way, I'm confused by your use of references to pass simple strings. It's making the code needlessly complex and error-prone. To add to the confusion, you use the same var names for the references as the actual vars!