Dear Monks,
I am having a bit of a problem with the following code--I am creating a tied scalar on the fly from within the FETCH method of a tied hash, and trying to return that tied scalar. I can get the tied scalar to be returned with a bit of cleverness, but then the tied scalar appears to no longer be tied. Even though ref tells me that it is a 'Tie::Scalar', but tied returns undef meaning it's not tied. For further wackiness, I can manually call $tied_scalar->FETCH on the tied scalar and it works, but just $tied_scalar does not automatically call fetch. Would anyone happen to know what is going on here and how I can keep the tied scalar from untying itself?

The general idea I'm trying to get working:

tie our %conf, 'My::Hash';
# $dir is a tied Tie::Scalar
our $dir = $conf{'dir'};
print $dir, $/;
# prints /home/foo for example

# using tie magic, storing a value in $dir also updates
# 'dir' in %conf
$dir = '/somewhere/else';
$dir = $conf{'dir'};
print $dir, $/;
# now prints /somewhere/else
[download]

I want %conf to be a general wrapper that can be treated like a hash, so tie seems like the way to go. I also want to fetch values from %conf, store them in scalars, and then when those scalars are changed I would like transparent changes to occur back in the tied hash. Kind of confusing, I know. But I need it this way, so lets just suspend alternative designs and look at it as a pure exercise in Perl.

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;
[download]

Now using the above code something unexpected happens:

tie our %conf, 'My::Hash';
our $dir = $conf{'dir'};
print ref $dir, $/;
# prints 'My::Scalar';
print tied $dir ? 1 : 0;
# prints 0
print $dir, $/;
# prints 'My::Scalar=HASH(0x820f268)'
print $dir->FETCH
# prints '/home/foo';
# attempts to call $dir->STORE give lvalue errors
#
# why is $dir untied now yet I can still call tied methods
# on it?
[download]

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