Ok. After some experimentation, I've got the following package:

Update: Version 2.0

use strict;

package MyTie;

my @TIED;

sub TIEHASH {
    my $type = shift;
    my $index = shift;

    return undef unless $TIED[$index];

    my $self;
    if ($TIED[$index]) {
        $self = $TIED[$index];
    } else {
        $TIED[$index] = $self = {};
        bless $self, ref($type) || $type;
    }

    $self->{HASH} = {};
    @{$self->{HASH}}{@_} = @{$self->{ARRAY}};
    $self->{ISTIED}{HASH} = 1;

    return $self;
}

sub TIEARRAY {
    my $type = shift;
    my $index = shift;

    my $self;
    if ($TIED[$index]) {
        $self = $TIED[$index];
    } else {
        $TIED[$index] = $self = {};
        bless $self, ref($type) || $type;
    }

    $self->{ARRAY} = [ @_ ];
    $self->{ISTIED}{ARRAY} = 1;

    return $self;
}

sub FETCH {
    my $self = shift;
    my $key = shift;

    return undef unless defined $key;

    if ($key =~ /\D/) {
        return undef unless $self->{ISTIED}{HASH};
        return $self->{HASH}{$key};
    } else {
        return undef unless $self->{ISTIED}{ARRAY};
        return $self->{ARRAY}[$key];
    }
}

sub STORE {
    my $self = shift;
    my $key = shift;

    return undef unless defined $key;

    if ($key =~ /\D/) {
        return undef unless $self->{ISTIED}{HASH};
        $self->{HASH}{$key} = shift;
    } else {
        return undef unless $self->{ISTIED}{ARRAY};
        $self->{ARRAY}[$key] = shift;
    }
}

sub FETCHSIZE {
    my $self = shift;

    return $#{$self->{ARRAY}};
}

1;

__END__
[download]

It's obviously not complete, as most of the ARRAY and HASH functions aren't included. They're relatively easy to do, according to the model.

To create a MyTie, I used the following:

#!/usr/local/bin/perl

use strict;
use warnings;

use MyTie;

my $index = 0;

my @blah;
tie @blah, "MyTie", $index, (5, 4, 3, 2, 1);

my %blah;
tie %blah, 'MyTie', $index, qw(zero one two three four);

print "$blah[2]\n";
print "$blah{two}\n";
[download]

Now, to extend this so you can have more than one MyTie, you have to decide how you're going to construct this. One possibility is to do the following:

1. Have a package global of a list in MyTie.
2. Always construct the array first.
3. Make the first element in the list some $index in that global array.
4. pop that index off before putting it into $self->{ARRAY}.
5. When creating the HASH part, put a index => $index.

Yet another thing to add is to create the array first, then create the hash by only passing the keys in as a list and creating the hash on the fly. I suspect this is what you want more. (Done in v2.0)

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