title: Running only one Perl script instance by cron
body: <p>I need to run Perl script by cron periodically (~every 3-5 minutes). I want to ensure that only one Perl script instance will be running in a time, so next cycle won't start until the previous one is finished. Could/Should that be achieved by some built-in functionality of cron, Perl or I need to handle it at script level? </p>
  
  <p>I am quite new to Perl and cron, so help and general recommendations are appreciated.</p>