...a "cell" in an array of array. e.g. @unique_manufacturer_model->[$i][12]++

(my emphasis)

A couple of points. The @ should be $ (think singlular, scalar, $) and you don't need the arrow (you have an array and the arrow is trying to dereference a reference to an array). If you had strict and warnings enabled Perl would have complained about it.

It would be well worth straightening out these snags first. Perl will help you if you turn on strict and warnings. :-)

update: fixed typo