package foo;

use strict;

sub new {
    bless [], ref $_[0] || $_[0] || __PACKAGE__;
}

sub declare {
    my $self = shift;

    ## auto vivification fails to make the correct indexes
    $self->[0] = {} unless $self->[0];

    no strict 'refs';

    foreach my $name (@_) {
        ## create the index reference
        $self->[0]{$name} = @$self;

        ## create a nicely named index variable
        ${ref($self) . '::' . $name . '_idx'} = @$self;

        ## create the accessor/mutator methods
        (my $code = 'sub { $_[0][VALUE] }') =~ s/VALUE/scalar @$self/e;
        *{ref($self) . '::get_' . $name} = eval $code;
        ($code = 'sub { $_[0][VALUE] = $_[1] }') =~ s/VALUE/scalar @$self/e;
        *{ref($self) . '::set_' . $name} = eval $code;

        ## create the (unitialized) attribute itself
        push @$self, undef;
    }
}