my %hash = (
    Mouse => {Index => 0, Value => 'Jerry'},
    Cat   => {Index => 1, Value => 'Tom'},
    Dog   => {Index => 2, Value => 'Spike'}
);

##</code><code>##

my $hash = {
    Mouse => {Index => 0, Value => 'Jerry'},
    Cat   => {Index => 1, Value => 'Tom'},
    Dog   => {Index => 2, Value => 'Spike'}
};

##</code><code>##

foreach (sort {$hash{$a} {'Index'} cmp $hash{$b} {'Index'}} keys %hash)  

##</code><code>##

$hash->{$a}