#!/usr/bin/perl

use strict;
use warnings;

# Make a copy of a variable

my $counter = 0;
print "Copying and replacing the variable\n";
for (1..10) {
    $counter = increment_number( $counter );
    print "Count is $counter\n";
}

$counter = 0;
print "Passing a reference to the variable\n";
for (1..10) {
    increment_number( \$counter );
    print "Count is $counter\n";
}

sub increment_number {
    my $number = shift;

    if (ref $number eq 'SCALAR') {
        $$number++;
        return;
    }
    return ++$number;
}