Graphviz and Friends

my $grammar = Marpa::R2::Scanless::G->new(
    {   action_object  => 'My_Nodes',
        default_action => '::first', # '::first' is a reserved word.
        source         => \(<<'END_OF_SOURCE'),
:start ::= Expression
Expression ::= Term
Term ::=
      Factor
    | Term '+' Term action => do_add
Factor ::=
      Number
    | Factor '*' Factor action => do_multiply
      Number ~ digits
      digits ~ [\d]+
      :discard ~ whitespace
      whitespace ~ [\s]+
END_OF_SOURCE
    }
);