package My::Hash;
use base 'Tie::Hash';

our %hash = ('dir' => '/home/foo');

sub TIEHASH {
  return bless \%hash, __PACKAGE__;
}

sub STORE {
  my ($self, $key, $val) = @_;
  $self->{$key} = $val;
}

sub FETCH {
  my ($self, $key) = @_;
  my $val = $self->{$key};
  tie my $tied_scalar, 'My::Scalar', $key, $val;
  return $tied_scalar;
}
1;

package My::Scalar;
use base 'Tie::Scalar';

sub TIESCALAR {
  my ($self, $key, $val) = @_;
  return bless {'value' => $val,
                'key' => $key ,
                'fetched' => 0
               }, __PACKAGE__;
}

sub STORE {
  my $self = shift;
  my $newval = shift;
  my $key = $self->{'key'};
  My::Hash::hash{$key} = $self->{'value'} = $newval;
}

sub FETCH {
  my $self = shift;
  # this cleverness is done so that Tie::Hash FETCH does not
  # call Tie::Scalar FETCH when it tries to return the tied
  # scalar.
  if ($self->{'fetched'}) {
    return $self->{'value'};
  }else{
    $self->{'fetched'} = 1;
    return $self;
  }
}
1;