sub desc_sort_salary {
   $salary{$b} <=> $salary{$a};  # Reverse $a and $b
}

%salary = (
        "P"  => 10,
        "S"  => 12,
        "C"  => 5,
        "S"  => 6,
        "L"  => 11,
        "D"  => 8,
);
foreach $key (sort desc_sort_salary(keys(%salary))) {
   printf "\t% -20s%5d\n", $key, $salary{$key};
}