It looks like an unnecessary obfuscation. How about this instead...

package PreserveWD;
use strict;
use Cwd qw(cwd);

sub new {
  my $class = shift;
  my $self = cwd;
  bless \$self, $class;
}

sub DESTROY {
  chdir ${+shift) or die "Cannot restore directory\n";
}
[download]

I think this is the model that SelectSaver uses. Yup. Similar code.

-- Randal L. Schwartz, Perl hacker