How to write cron jobs in perl?

Most Unix systems are set up to run "housekeeping chores" such as log-rotation, unused files deletion, indexing local files for the search engine, etc. With cron these tasks are, often, scheduled to be executed overnight or another low-usage time to avoid straining the system. If the system is turned off at the time a given task should have been run, it will not be executed for that iteration.