#!/usr/bin/perl

use strict;
use warnings;

use Test::More tests => 5;
use Parse::RecDescent ();

my $p = Parse::RecDescent->new(<<'__END_OF_GRAMMAR__');

{
   use strict;
   use warnings;
}

parse    : rec /\Z/ { $item[1] }
rec      : POS_INT rec_list[ $item[1] ] { [ $item[0] => $item[2] ] }
rec_list : { $arg[0] == 0 ? [] : undef }
         | ELEM rec_list[ $arg[0]-1 ] { [ $item[1], @{$item[2]} ] }
POS_INT  : /\d+/
ELEM     : /\S+/

__END_OF_GRAMMAR__


ok($p->parse('0'));
ok($p->parse('1 foo'));
ok($p->parse('2 foo bar'));
ok(!$p->parse('1'));
ok(!$p->parse('1 foo bar'));