Store Related Values Together

Storing related items together means you manage one array instead of many
Suppose you want to discard some items?
With parallel arrays:

        for (grep {$size[$_] == 0} (reverse 0 .. $#size)) {
          splice @size, $_, 1;
          splice @user, $_, 1;
          splice @group, $_, 1;
          splice @time, $_, 1;
        }

Better hope you didn't forget to splice one of the arrays!
With a single array, the arrays never get out of sync:

        @rec = grep {$_->{size} != 0} @rec;