#!/usr/bin/perl --
use Parse::RecDescent;

my $grammar =
q(
myrule : <rulevar: local $failed>
myrule : 'stuff' mysubrule(?) <reject: defined $failed> { print "WHAT ($failed)!\n"; undef }
| <error>
mysubrule: 'ID' <commit> '[' ']'
| <error?> { $failed++ }
);


my $parser = Parse::RecDescent->new($grammar) or die "hi";
for my $text (
    "stuff ID something",
    "stuff  something",
){
    print "text => $text\n";
    my $tree = eval { $parser->myrule($text) };
    warn $@ if $@;
    use Data::Dump qw/ dd /; dd $tree;
}

__END__
text => stuff ID something
WHAT ()!

       ERROR (line 1): Invalid mysubrule: Was expecting '[' but found
                       "something" instead

       ERROR (line 1): Invalid myrule: Was expecting 'stuff'
undef
text => stuff  something

       ERROR (line 1): Invalid myrule: Was expecting 'stuff'
undef