use strict;
use warnings;

my %employees = (
    '1' => {
        boss_id => '1',
        emp_name => 'big boss',
    },

    '2' => {
        boss_id => '1',
        emp_name => 'middle boss',
    },

    '3' => {
        boss_id => '2',
        emp_name => 'worker 1',
    },

    '4' => {
        boss_id => '1',
        emp_name => 'small boss',
    },

    '5' => {
        boss_id => '2',
        emp_name => 'worker 2',
    },
    
    '6' => {
        boss_id => '4',
        emp_name => 'worker 3',
    },
);

getreports(1);

sub getreports
{
    my ($id, $level) = @_;
    $level = $level || 0;
    die "Employee $id doesn't exist" if ! exists $employees{$id};

    print ' ' x ($level * 3), "|\n",
          ' ' x ($level * 3), "+- $employees{$id}{emp_name}\n";

    my @employees = ();
    foreach my $emp_id (keys %employees) {

        # find the employees under $id except
        # when boss is himself

        push @employees, $emp_id
            if $employees{$emp_id}{boss_id} eq $id &&
               $emp_id ne $id;
    }

    return if $#employees < 0;

    getreports($_, $level + 1) foreach (@employees);
}

##</code><code>##

|
+- big boss
   |
   +- small boss
      |
      +- worker 3
   |
   +- middle boss
      |
      +- worker 1
      |
      +- worker 2