my $root = {};
my $node = $root;
my @stack;
while (<DATA>) {
  chomp;
  if (/^\s*BEGIN\s+(.*)/) {
    my $child = {};
    $child->{_type} = $1;
    push(@{$node->{_children}}, $child);
    push(@stack, $node);
    $node = $child;
  } elsif (/^\s*END\s+(.*)/) {
    # check: $node->{_type} eq $1
    $node = pop(@stack);
  } elsif (/^\s*(\S+)\s+(.*)/) {
    # remove quotes from $2 here?
    $node->{$1} = $2;
  } else {
    die "unexpected input: $_"
  }
}

use Data::Dumper;
print Dumper($root);