programming-examples/perl/Subroutine/A subroutine is defined by the sub keyword and the block of code that follows.pl

    #!/usr/local/bin/perl -w

    # Declare the subroutine named usage
    sub usage
    {
       my ($program, $exitCode) = @_;

       print "Usage: $program [-v] [-h]\n";
       exit $exitCode;
    }

    usage ($0, 1);