use Data::Dumper;
use strict;
use warnings;

my %h = ( foo => 1 );

{
local $h{'foo'} = 2;
print Dumper \%h;
}

print Dumper \%h;

##</code><code>##

$VAR1 = {
          'foo' => 2
        };
$VAR1 = {
          'foo' => 1
        };