#!/usr/bin/perl

use strict;
use warnings;

run();

sub run
{
    my $arr1 = [0 .. 12];
    my $arr2 = ['a' .. 'l'];

    print "before:\n";
    print "arr1 = @{$arr1}\n";
    print "arr2 = @{$arr2}\n";

    # because we're passing references to arrays, any changes
    # made to the arrays in the subroutine will affect the arrays
    # here as well. No need to return the arrays.
    f($arr1, $arr2);

    # use the arrow operator and square brackets to index the
    # array, same as in the subroutine below - same syntax,
    # less confusing
    $arr1->[7] = "SEVEN!";

    print "after:\n";
    print "arr1 = @{$arr1}\n";
    print "arr2 = @{$arr2}\n";
}

sub f
{
    my ($arr1, $arr2) = @_;

    for (my $i = 0; $i < 5; $i++)
    {
        # shuffle some stuff around
        my $index1 = rand($#$arr1);
        my $index2 = rand($#$arr2);

        # use the arrow operator and square brackets to index
        # the array through a reference
        my $tmp = $arr1->[$index1];
        $arr1->[$index1] = $arr2->[$index2];
        $arr2->[$index2] = $tmp;
    }
}