SGI::FAM seems like a more compatible and less linux-only solution, and fam should run on Mac Os X (and BSDs of all stripes really, as it can be compiled to run with kqueue

Update: Maybe that is not such a good recommendation, SGI::FAM depends on deprecated File::PathConvert, has an unregistered dependency on Test::Helper and doesn't find my libfam without help.
After that, it does seem to work, though, quite well, though only on famd started as a daemon, not running through inetd.