This just seems like a fancy wrapper to $instance->{attribute} notation. Yeah, you can make assignments to more complicated things, but you can do that with overload as well. I guess I just don't get it.

I've fallen in the habit of implementing this type of thing for set and get operations:

package SomePackage;
use base 'Class::Base';

## super-simple 'new'
sub new {
   my $self = shift;
   bless { one => 1, two => 2 }, $self;
}

sub set {
   my $self   = shift;
   my $attrib = shift;
   return $self->error("No such attribute '$attrib'") 
      unless exists $self->{$attrib}
   
   my $value = shift;
   # check to make sure we're setting the same kind of reference, if i
+t matters
   if (ref $self->{$attrib} && ref $value ne ref $self->{$attrib}) {
      return $self->error("Reference types do not match for '$attrib' 
+set.")
   }

   $self->{$attrib} = $value;
   return 1; # true on success   
}

sub get {
   my ($self, $attrib) = @_;
   return $self->error("Attribute '$attrib' doesn't exist")
     unless exists $self->{$attrib};
   
   my $value = $self->{$attrib};
   return $value;
}

1;
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This means I can do $instance->set('one', 'Hey there!'); and $instance->get('two');. If certain attributes have special rules to validate data, I can deal with those by altering 'set' slightly. For example:

# set from above gets renamed _set_DEFAULT

sub set {
   my ($self, $attrib, $value) = @_;
   if ( $self->can('_set_'.$attrib) ) {
      my $result;
      eval "\$result = \$self->_set_$attrib($value)";
      return $result;
   }
   else {
      return $self->_set_DEFAULT($attrib, $value);
   }
}
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Something like that is much cleaner and clearer in the implmentation. I like the idea that when I see $instance->{attrib} = 2, I know the code is messing about with something advanced, while $instance->set('attrib', 2) is playing by the rules.

Besides, with Perl6's advancements in lvalue subs, it will be possible to do something like $instance->accessor('attrib') = 2, and we both win, so I don't see much point in debating the tie methodology.