I think you should use an array of workbooks. You'll end up with an array of arrays of hashrefs, or something similar, but I suppose it should not be a big problem since you're already using hashrefs in your code.

Whenever you start naming variables $var1, $var2, ..., $var5, this is signal that there is probably something wrong with your code and that you should probably have a @var array instead, with the values stored in $var[0], $var1, etc.