use strict;
use warnings;
use DBI;

my $tmpFileName = 'temp';
open my $outFile, '>', $tmpFileName or die "Can't open $tmpFileName: $!\n";
print $outFile $_ for <DATA>;
close $outFile;

my $dbh = DBI->connect ("DBI:CSV:")
    or die "DBI connect failed: $DBI::errstr";
my $sth = $dbh->prepare ("SELECT * FROM temp");
my @structure;
my %idMap;

$sth->execute ();
while (my $row = $sth->fetchrow_hashref) {
    my ($id, $name, $parent) = @{$row}{'id', 'name', 'parent'};

    if (! $parent) {
        push @structure, {id => $id, name => $name, children => []};
        $idMap{$id} = $structure[-1];
        next;
    }

    if (exists $idMap{$parent}) {
        push @{$idMap{$parent}{children}}, {id => $id, name => $name, children => []};
        $idMap{$id} = $idMap{$parent}{children}[-1];
        next;
    }

    die "Can't handle children id provided before parent";
}
$sth->finish     ();
$dbh->disconnect ();

print dumpChildren($_) for @structure;


sub dumpChildren {
    my ($node, $indent) = @_;

    $indent ||= '';

    my $str = "$indent$node->{name}\n";

    $indent .= '   ';
    $str .= dumpChildren ($_, $indent) for @{$node->{children}};
    return $str;
}


__DATA__
id,name,parent
1,data1,0
2,data2,1
3,data3,1
4,data4,3
5,data5,4

##</code><code>##

data1
   data2
   data3
      data4
         data5