Familiarity with POSIX and/or C can help in knowing what to look for. You're interested in stat for retrieving file information, or possibly the -M operator (documented in perlfunc as well, type perldoc -f -X at your shell prompt). And File::Find or File::Find::Rule will help you traverse your filesystem to get the victim directories' names. File::Path has routines for blowing away directory trees, but it may be just as simple to shell out to rm -rf ./blah via system.