In my experience, the perl script file is not held open once it is executing. I've saved a changed file without error while a script was running. Modules that modify itself, like the pony thing or bleach, rely on being able to rewrite the current file, so I'm sure it's not just an NT implementation thing. Those wierd modules operate inside a
, which means the file must be closed before parsing starts, rather than read and parsed a line at a time.