Unproductive symbol: digits at test.pl line 7

test.pl

package Parse::ProductName;
use Marpa::R2;

sub new {
    my($class) = @_;

    my $grammar = Marpa::R2::Scanless::G->new({
            action_object => 'Parse::ProductName::Actions',
            default_action => 'do_first_arg',
            source => \<<'SOURCE'

:start          ::= product_name

product_name    ::= sku
                  | name name digits              action => do_list

sku              ~  digits '/' digits

digits           ~ [\d]+

name             ~ [a-zA-Z]+

:discard         ~ ws
ws               ~ [\s]+

SOURCE
    });

    my $self = {
        grammar => $grammar,
    };
    bless $self, $class;
    return $self;
}

sub parse {
    my $self = shift;
    my $input = shift;
    my $re = Marpa::R2::Scanless::R->new({grammar => $self->{grammar}});
    $re->read(\$input);
    return ${$re->value};
}

package Parse::ProductName::Actions;
use strict;

sub new {
    my $klass = shift;
    return bless {}, $klass;
}

sub do_first_arg {
    shift;return $_[0];
}

sub do_list {
    shift; return \@_;
}

package main;

my $p = Parse::ProductName->new;
$p->parse("name 100");