{
    package foo;
    use Tie::IxHash;
    tie(my %h, 'Tie::IxHash', qw(one two three four));

    sub new { bless { val => \%h } }
    sub val : lvalue  { $_[0]->{val}->{one} }
}
use Data::Dumper;
my $obj =  foo->new;
print Dumper( $obj );

__output__

$VAR1 = bless( {
                 'val' => {
                            'one' => 'two',
                            'three' => 'four'
                          }
               }, 'foo' );