#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use Storable qw(dclone freeze thaw);

my $href = undef;

$href = { 'a' => { 'status' => 'OK' }};
print "BEFORE SUB: " . $href->{a}->{status} . "\n";

do_stuff($href);
print "AFTER SUB: " . $href->{a}->{status} . "\n";


sub do_stuff {
    
    my $hash = shift;
    my $hash2 = freeze($hash);
    $hash->{'a'}->{'status'} = "NOT OK";
    
    $hash = thaw($hash2);
    print "IN SUB: " . $hash->{'a'}->{'status'} . "\n";
    return 0;
}

##</code><code>##

$ ~/test.pl 
BEFORE SUB: OK
IN SUB: OK
AFTER SUB: NOT OK