#!perl

use strict;
use warnings;

sub returnParsed {
   my ($array, $index, $level) = @_;
   my $levelhash = {};
   while ($index < @$array) {
      last if ($array->[$index]->{'level'} < $level);
      if ($array->[$index]->{'level'} == $level) {
         $levelhash->{$array->[$index]->{'department'}}
            = returnParsed($array, $index + 1, $level + 1);
      }
      ++$index;
   }
   return $levelhash;
}

sub dumpSorted {
   my ($structure, $indent, $startindent) = @_;
   my $dumped = '';
   for (sort keys %$structure) {
      $dumped .= " " x $startindent . "$_\n";
      $dumped .= dumpSorted($structure->{$_}, $indent, $startindent + $indent);
   }
   return $dumped;
}

my  @array = ({ level => 1, department => 'Office of President', },
{ level => 2, department => 'Recruiting', },
{ level => 2, department => 'Software', },
{ level => 3, department => 'MIS', },
{ level => 3, department => 'System Operations', },
{ level => 2, department => 'Pipe line', },
);

print dumpSorted(returnParsed(\@array, 0, 1), 3, 3);