How long to sleep depends on the granularity of what you need. If the file gets deleted and you need to do something immediately, then a small sleep. If you just generally need to know it, perhaps a sleep 300 or <code>sleep 600<code> for 5 or 10 minutes would be appropriate. If you need to do something by the next day, sleep for an hour or more, who cares.

However, if your delay is big, a better answer might be to use a scheduler to run you check program instead of idle in the background. On a *nix box use cron, not sure on Win32 box. This isn't as worthwhile with a small delay because of the overhead of loading Perl.

While this may not use much CPU resources, since you are doing I/O, it is also using disk resources. I'd set the delay as long as you can stand.

=Blue
...you might be eaten by a grue...