I thought deep copy of hash of hash would work, but when I modify the originla hash %x, the deep copy %y is modified too. What do i did wrong ?

my %x= ('miller'=> {'lastname' => 'michael','tel'=>'222'},
        'duran' => {'lastname'=> 'peggy', 'tel' => '333'},
    );

print "--Original hash \n";
for my $nom  (keys %x) {
    print "nom: ", $nom, " ";
    for my $val (keys %{$x{$nom}} ) {
        print $val, ": ", $x{$nom}{$val}, " ";
    }
    print"\n";
}
my $y= {%x};  #anonymous hash ref containg data freom %x
#
#modifying $x shouldn't affects $y ??
#
$x{'duran'}{'tel'}='888';

print "--Deep copy of Original hash \n";
#notice how to dereference $y !!
for my $nom (keys (%$y)) {
    print "nom: ", $nom, " ";
    for my $val (keys %{@$y{$nom}}) {
        print $val, ": ", $y->{$nom}{$val}, " ";
    }
    print "\n";
}

</h3>
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And the code prints this (unexpected) :

--Original hash
nom: miller lastname: michael tel: 222
nom: duran tel: 333 lastname: peggy
--Deep copy of Original hash
nom: duran tel: 888 lastname: peggy
nom: miller lastname: michael tel: 222
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