How about you mutate that into some stand alone code with a sample of the data you are trying to process so we can reproduce your issue?

While you are doing that there are a number of areas where it would be to your advantage to make your code less like C and more like Perl and clean to up a few other style issues:

• Use Perl for loops where you can: for my $row (@rows) { my @values = split /\,/, $row;
• declare and initialise variables at the same time: my @fields = split /\,/, $rows[0];
• Filter your array directly: @rows = grep {defined} @rows;.

Actually the last point may be related to your undef issue. If some of the first $rowCount elements in @rows are undef you will get warnings. You will also get warnings if there are too few values in a row.