I'm trying to sort on the first two columns

sub RowSort {

    my($a1, $a2) = $a =~ /(\d+),(\d+)/;         
    my($b1, $b2) = $b =~ /(\d+),(\d+)/;         

    $a2 <=> $b2 or $a1 <=> $b1;
}
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Chaining comparisons with 'or' has the effect that if the first one says 'equal' (<=> yields 0), the next comparison is being tested, etc.