This might seem extensive but the recursion will fetch you all elements within any given HOH into a single array structure. Not sure if this is exactly your requirement..

$hash =
    {
        total_counts => tot_counts,
        words => {
                       nw => 1,
                 }
    };

@finalarray = get_array($hash);
print "@finalarray";

sub get_array {
    my($hash) = @_;
    my $array = [];
    if(ref $hash eq 'HASH') {
        foreach (keys %$hash) {
            if(ref $hash->{$_} eq 'HASH') {
                push @{$array} , $_;
                push @{$array} , get_array($hash->{$_});
            }
            else {
                push @{$array} , $_;
                push @{$array} , $hash->{$_};
            }
        }
    }
    return @$array;
}