code.pl

use strict;
use warnings;
use feature qw(say state);

use List::Util qw(sum0);

sub sliced { my ($arr, @i) = @_; @i = grep 0<=$_ && $_<@$arr, map int, @i; @{$arr}[@i] }

sub make_tree {
    my $list = shift;
    my ($nchild, $ndata) = splice @$list, 0, 2;
    my @children = map make_tree($list), 1..$nchild;
    my @data = splice @$list, 0, $ndata;
    return [ \@data, @children ];
}

sub sum_data {
    my $node = shift;
    my ($data, @children) = @$node;
    return sum0(@$data)
         + sum0(map sum_data($_), @children);
}

sub value_of {
    my $node = shift;
    my ($data, @children) = @$node;
    return @children
      ? sum0(map value_of($_), sliced(\@children, map $_-1, @$data))
      : sum0(@$data);
}

sub main {
    my @list = map int, split ' ', do { local $/; <> };
    my $root = make_tree(\@list);
    say sum_data($root);  # part 1
    say value_of($root);  # part 2
}

main;