#!/usr/bin/perl -w
use strict;
use Carp;
use Data::Dumper;

sub array_ref
{
    my $array_ref = shift;
    croak 'Not an array reference' unless ref($array_ref) eq 'ARRAY';

    print Dumper($array_ref);
}

my @array = qw/ 1 2 3 4 5 /;
my %hash = qw/ 1 1 2 2 3 3 4 4 5 5 /;

array_ref(\@array);
array_ref(\%hash);

##</code><code>##

$VAR1 = [
          '1',
          '2',
          '3',
          '4',
          '5'
        ];
Not an array reference at try.pl line 9
        main::array_ref('HASH(0x81d4e14)') called at try.pl line 18