PEG style ranking

try2.t

#!perl
use strict;
use warnings;
use 5.010;
use Data::Dumper;
use Marpa::R2;

sub My_Actions::dwim {
    shift;
    return $_[0] if scalar @_ == 1;
    return join '', '(', @_, ')';
}

# This grammar tries to be equivalent to a PEG or Regex with ordered choice:
# List: Item*
# Item: VAR = VAR // VAR = // VAR
# In order to force that "order", this grammar specifies "rank"s.
use constant BNF => <<'BNF';
  :default ::= action => My_Actions::dwim
  :discard ~ ws; ws ~ [\s]+
  
  List ::= Item rank => 2
  List ::= List Item rank => 1
  Item ::= VAR '=' VAR  rank => 3
  Item ::= VAR '='      rank => 2
  Item ::= VAR          rank => 1
  VAR ~ [\w]+
BNF

local $Data::Dumper::Terse = 3;

my $g = Marpa::R2::Scanless::G->new({ source => \BNF });

sub all_parses {
  my ($input) = @_;
  my $r = Marpa::R2::Scanless::R->new({ grammar => $g, ranking_method => 'high_rule_only' });


  $r->read(\$input);

  # say "Earley set: $_\n", $r->show_progress($_) for 1 .. 6;

  say "Input: $input";
  my $i = 0;
  while (my $value_ref = $r->value()) {
    $i++;
    say "Parse $i: ", Data::Dumper::Dumper($value_ref);
  }
  return $i;
}

all_parses("a = b");
all_parses("a = b c");
all_parses("a = b c = d");
all_parses("a = b c = d e");
all_parses("a = b c = d e =");
all_parses("a = b c = d e = f");