title: In Perl, what is the difference between a .pm (Perl module) and .pl (Perl script) file?
body: <p>What is the Difference between <code>.pm</code> (Perl module) and <code>.pl</code> (Perl script) file?</p>
  
  <p>Please also tell me why we return <code>1</code> from file. If return 2 or anything else, it's not generating any error, so why do we return <code>1</code> from Perl module?</p>