I don't think it's that easy and I do think the parent has a point. I mean, while you're busy writing a perl one-liner to munge on your file, ten daemons are writing to their log files, all on the same file system. You want to roll back the effects of your script doing an accidental rm ~/*, but not what's in the logs. Probably a better idea is to strace the shell's children and record changes, then apply or forget them.