Sort by value demo

my %hash = (
            'L3D0' => '3 0',
            'L3D7' => '3 7',
            'L13D0' => '13 0',
            'L13D1' => '13 1',
            'L13D7' => '13 7',
    );

my %hash_1;
while (my ($k, $v) = each(%hash)) {
    my @a = sort { $a <=> $b } split /[ ]/, $v;
    $hash_1{$k} = \@a;
}

sub sort_by_value {
    my ($k_a, $k_b) = @_;
    my @a = @{$hash_1{$k_a}};
    my @b = @{$hash_1{$k_b}};
    return (($a[0] <=> $b[0]) or ($a[1] <=> $b[1]));
}

my @sorted_keys = sort { sort_by_value $a, $b } keys %hash_1;

for my $k (@sorted_keys) {
    print $k, "=>", "@{$hash_1{$k}}", "\n";
}