What is the rule for printing? Maybe you want the following:

my @last_key;

for my $row (@$arr_ref) {
    local $" = "\0";
    my @curr_key = @{$row}[0,1];
    if ("@curr_key" ne "@last_key") { {
        @last_key = @curr_key;
        print join "\n", @curr_key;
        print "$row->[2]\n";
    } else {
        print ",", $row->[2];
    };
};
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There is one problem with my solution. I was too lazy to shield the code against \0 occurring in your data. If that is a possibility, you will have to modify my code to do a comparison by-element instead of relying on Perls stringification of arrays to do the magic.