As another suggestion, this $$xx[blah] notation is confusing. Here $row is a reference. I prefer the arrow notation. This makes it more clear that $row is a reference.

for my $row ( @{$serials}) 
{
        my $equ =    $row->[$equIndex];
        my $pmf =    $row->[$pmfIndex];
        my $pro =    $row->[$proIndex];
        my $serial = $row->[$serialIndex];
        my $usr =    $row->[$usrIndex];
        my $date =   $row->[$dateIndex];
        my $clean =  $row->[$cleanIndex];
        
        #blah.....
}
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