#!/usr/bin/perl -w
use strict;

{
    package FixedArrayOfScalarRefs;
    use Carp qw( croak );

    sub TIEARRAY {
        my ( $class, @refs ) = @_;

        my $self = [@refs];
        bless $self, $class;
        return $self;
    }

    sub FETCH {
        my ( $self, $index ) = @_;

        if ( not ref $self->[$index] ) {
            croak "Array index $index out-of-bounds";
        }

        my $value = ${ $self->[$index] };
        return $value;
    }

    sub STORE {
        my ( $self, $index, $value ) = @_;

        if ( not ref $self->[$index] ) {
            croak "Array index $index out-of-bounds";
        }

        ${ $self->[$index] } = $value;
    }

    sub FETCHSIZE {
        my ($self) = @_;

        return scalar @$self;
    }
}

##</code><code>##

my ( $a1z, $a2z, $a3z ) = qw( 42 13 666 );
my @az;

tie @az, 'FixedArrayOfScalarRefs',
    "There is no element zero!",  # Dummy element 0
    \( $a1z, $a2z, $a3z );        # Elements 1 .. 3

for ( 1 .. 3 ) {
    print "\$a${_}z = $az[$_]\n";
}

##</code><code>##

print "\$a0z = $az[0]\n"; 
# Array index 0 out-of-bounds at bar.pl line 63

##</code><code>##

use List::Util qw( sum );

my $sum = sum( @az[ 1 .. 3 ] );

print "sum = $sum\n";

##</code><code>##

my $sum = sum( @az );