$in = "sample.txt";
open (IN, $in) or die "cant open the in\n";
#
my %dict; # A reverse index on %dict by id.
#
my %dict; # A reverse index on %dict by id.
while (not eof (IN)) {
	$line = <IN>;
    my ( $id, $parent, $term ) = split (' ', $line, 3) ;

    $dict{$id}{'id'}     = $id;
    $dict{$id}{'parent'} = $parent;
    push @{$dict{$parent}{'children'}}, $dict{$id};
}

use Data::Dumper;
print Dumper( \ %dict );