0UT1S's

sub push {
  my ($self, $key, $val) = @_;
  push @{$self->{stack}{$key}}, $self->{values}{$key}
    if exists $self->{values}{$key};
  $self->{values}{$key} = $val;
}

sub pop {
  my ($self, $key) = @_;

my $val = delete $self->{values}{$key};
  if ( exists $self->{stack}{$key} ) {
    $self->{values}{$key} = pop @{$self->{stack}{$key}};
    delete $self->{stack}{$key} unless @{$self->{stack}{$key}};
  }

return $val;
}

sub values_set {
  my $self = shift;
  return undef unless ref($self);
  return $self->{values};
}

sub all_config {
  my $self = shift;
  my $v = ref($self) ? $self->{values} : {};
  return {%Config, %$v};
}