You can't turn the object referenced by $x into the object referenced by $z, except of course by assignment: $x=$z. You can however, rebless any reference into a new class:

use strict;
use warnings;

sub Eng::speak { print "I speak English\n"; }
sub Fr::speak { print "Je parle francais\n"; }

my $x=bless({},'Eng');
print "<$x>\n";  #prints: <Eng=HASH(0x814ec28)>
$x->speak();     #prints: I speak English


bless($x, 'Fr');
print "<$x>\n";  #prints: <Fr=HASH(0x814ec28)>
$x->speak();     #prints: Je parle francais
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As for proxy objects and lazy loading, there are numerous modules on CPAN for this purpose. See CPAN search: proxy object for starters.

Best, beth