synthetic

Eliminate Synthetic Variables

MJD would call $count in v0.43 a synthetic variable:

    an artifact of the way we solve the problem ... 
    inessential to the problem itself.

$count was useful for readability early in Data::Presenter's development.
But _count_engine() improves the readability so much that $count can now be eliminated.
Assuming there's no loss of readability, eliminating synthetic variables improves the code's readability.