use Data::Dumper;
$Data::Dumper::Sortkeys = 1;
$Data::Dumper::Indent   = 0;

my $args = {
    foo => 1,
    baz => 2,
};

print "Before calling mysub(\$args)\n";
print Dumper($args), "\n\n";

mysub($args);

print "After calling mysub(\$args)\n";
print Dumper($args), "\n\n";

sub mysub {
    my $args = shift;
    local $args->{'foo'} = $args->{'foo'};
    $args->{'foo'} += 100; # 101 now.
    print "Inside mysub()\n";
    print Dumper($args), "\n\n";
    othersub($args);
}

sub othersub {
    my $args = shift;
    local $args->{'baz'};
    delete $args->{'baz'};
    print "Inside othersub()\n";
    print Dumper($args), "\n\n";
}

##</code><code>##

Before calling mysub($args)
$VAR1 = {'baz' => 2,'foo' => 1};

Inside mysub()
$VAR1 = {'baz' => 2,'foo' => 101};

Inside othersub()
$VAR1 = {'foo' => 101};

After calling mysub($args)
$VAR1 = {'baz' => 2,'foo' => 1};