Counting layers

use lib './' ;
use CSV_PP 'csv';
my $employees = csv ({ in => *STDIN, key => "posnum"});
my $levels = 0 ;
my $message = qq{Please see Section 5.1 of the Directive.\n} ;

for (sort keys %$employees) {
    do {
        print "$_ ";
        $_ = $employees->{$_}{"supposnum"};
        $levels++;
    } while defined ;
    $levels--;
    print $levels == 1 ? "--- $levels level" : "--- $levels levels" ;
    print $levels  > 3 ? "\nYou have $levels layers. $message" : "\n" ;
    $levels = 0 ;
}