#!/usr/bin/perl -w
use strict;
use warnings;
use Tie::Hash;

our %nottied = ('a'..'d');
tie our %tied, "Tie::StdHash";
%tied = ('a'..'d');

print "tied is: ", %tied, "\n";
print "nottied is: ", %nottied, "\n";

$_ = "x" for &{sub { values %tied }};
$_ = "x" for &{sub { values %nottied }};

print "tied is now: ", %tied, "\n";
print "nottied is now: ", %nottied, "\n";
__END__
output is:

tied is: cdab
nottied is: cdab
tied is now: cxax
nottied is now: cdab