use strict; use warnings; use Data::Dumper;

sub proc{
	my($pre, $cnt_cur, $end_brackets)=@_;
	my $buff;
	
	$buff = $pre->{data} ;
	if ($cnt_cur > $pre->{cnt}){		#next is children
		$buff .=' => {';
		push(@$end_brackets, '}');
	}elsif ( $cnt_cur == $pre->{cnt} ){	#next is brothers
		$buff .= ' => undef ,';
	} else {							
		$buff .=  ' => undef ,';
		for ( 1 .. ($pre->{cnt} - $cnt_cur) ){	#output right bracket till that depth
			$buff .= pop(@$end_brackets) . ",";
		}
	}
	return $buff;
}

my ($pre, $cnt, $ret, @end_brackets);
$ret='{';
while(<DATA>){
	
	$cnt = $_ =~ s/\s{4}//g;
	$cnt = $cnt || 0;
	
	if ( $pre  ){
		$ret .= proc($pre, $cnt, \@end_brackets);
	}
	
	$pre={cnt => $cnt, data=>$_};
}
$ret .= proc($pre, 0, \@end_brackets);
$ret .= '}';

print Dumper eval($ret);

__DATA__
one
    two
    three
        four
    three_another
        four_another
five
    six
seven
    eight
        nine
            ten
11
    12
    13
    14
    15
16
    17
        18
            19
        20
    21
        22
            23
                24