# traverse($hoh, @key): return value of $hoh->{$key[0]}...{$key[-1]}
sub traverse {
  my $hoh = shift;
  $hoh = $hoh->{$_} for (@_);
  $hoh
}

# set($hoh,$val, @path): ...
sub set {
  my $hoh = shift;
  my $val = shift;
  my $last = pop @_;
  $hoh = $hoh->{$_} for (@_);
  $hoh->{$last} = $val
}