$ARG does not exist If you read the perlvar perldoc (perldoc perlvar or https://perldoc.perl.org/perlvar https://perldoc.perl.org/perlvar), you will see it is

$ARG does not exist If you read the perlvar perldoc (perldoc perlvar or https://perldoc.perl.org/perlvar https://perldoc.perl.org/perlvar), you will see it is the English form of $_. You just need to: use English;