I don't get it, tokenizer/lexer works, but the parser doesn't ( no parse tree), what am I missing?

#!/usr/bin/perl --
use strict; use warnings;
use HOP::Parser qw/:all/;
use HOP::Lexer ();
my @tokens = (
    [ 'RO',   qr/ro/i, ],
    [ 'SHAM', qr/sham/i, ],
    [ 'BO',   qr/bo/i, ],
#~     [ 'SPACE',   qr/\s+/i, sub{()}],
);
my $RoShamBo = star(
  alternate(
    lookfor('RO'),
    lookfor('SHAM'),
    lookfor('BO')
  ),
);
my $entire_input = concatenate( $RoShamBo, \&End_of_Input, );
use Data::Dump qw/ dd pp /;

my $lexer = HOP::Lexer::string_lexer( q{ RO SHAM BO }, @tokens );
print "tokenizer/lexer works\n";
while ( my $token = $lexer->() ) {
    dd $token;
}

print "\nbut parser doesn't work\n";
$lexer = HOP::Lexer::string_lexer( q{ RO SHAM BO }, @tokens );
if (my ($result, $remaining_input) = eval { $entire_input->($lexer) } 
+) {
  dd [ results => $result, remainder => $remaining_input ];
} else {
  print "Parse error. $@ ", pp($@), "\n";
}
__END__

tokenizer/lexer works
" "
["RO", "RO"]
" "
["SHAM", "SHAM"]
" "
["BO", "BO"]
" "

but parser doesn't work
Parse error. ARRAY(0xa6b164) ["End of input", sub { ... }]
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