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];
    };
};