$ExcelLink = &swOpenExcel( .. 21 variables .. );

sub swOpenExcel { ## I assume
    ( ... 19 variables ... ) = @_;
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That is going to cause you some severe problems.

I would also recomend you rename $rVals, $X, and $Y to something like $rVals_ref, $X_ref, and $Y_ref just to remind you that you are using refs into the future.