Offering an object-oriented version (Taking some liberties offered by perl over "strict OO"): 
#!/usr/bin/env perl

use strict;
use warnings;
{package Item;
  my %By_id; # Collection
  sub new{
    my ($class,%attr) = @_;
    die "ID is required" unless $attr{id};
    return $By_id{$attr{id}}=bless \%attr, $class;
  }
  sub GetParentObj{
    return undef if $_[0]->{parent} eq "#"; # Root has no parent 
    return $By_id{ $_[0]->{parent} };
  }
  sub GetRoot{ # CLASS method 
    return $By_id{"#"};
  }
  sub GetChildren{
    my ($self) = @_;
    return grep {$_->{parent} == $self->{id}} values %By_id;
  }
  sub GetAncestors{
    my ($self) = @_;
    my @ancestors;
    my $parent = $self; 
    while ($parent = $parent->GetParentObj()){
        push @ancestors, $parent;
    }
    return @ancestors;
  }
  sub GetAll{ # CLASS method
    my ($sort_att) = @_;
    $sort_att ||= "name"; # Defaults to name-based 
    return sort {$a->{$sort_att} cmp $b->{$sort_att}  } values %By_id;
  }
}
# -- Main Code -----
while (<DATA>) {
    chomp;
    my ($id, $pid, $name) = split /,/;
    Item::->new(id=>$id, parent=>$pid, name=>$name);
}

for my $item (Item::GetAll("name")){
  print $item->{name},
        map({"," . $_->{name}} $item->GetAncestors()),
        "\n";
}
__DATA__
15,10,name3
10,#,name1
12,10,name2
5,12,name4
8,5,name5

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                As a computer, I find your faith in technology amusing.

In reply to Re: Reorganizing the content of a file by NetWallah
in thread Reorganizing the content of a file by ovedpo15

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