#! /usr/bin/perl

use strict;
use warnings;
use Data::Dumper;
use Hash::Util qw(lock_keys);

my %hash = (test => {key => 1, kes => 2},
            test2 => {key => 1, kes => 2},
           );

lock_keys(%{$hash{test2}});

$hash{test}->{uhu} = 1;
print Dumper(\%hash);

$hash{test2}->{uhu} = 1;
print Dumper(\%hash);