Perl is case sensitive. Here is an SSCCE:

use strict;
use warnings;

use Test::More tests => 2;
use Clone 'clone';

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

$x{duran}{tel} = '444';
isnt ($x{duran}{tel}, $y{duran}{tel});
[download]