Parse::Marpa - first results

I just found the parser generator mentioned above on CPAN and played with it (some usage rules I've found so far will be mentioned in the next post). The following source is intended to decompose the well-known ambiguous english sentence "fruit flies like a banana", the output is appended below. Marpa does this, but finds 8 results instead of 2 (each of the interpretations is found 4 times). Since this is my first trial, I believe the fault is in my program.

#!/opt/bin/perl

use 5.011;
use strict;
use warnings;
use English qw(-no_match_vars);
use Parse::Marpa;

my $grammar_description='
start symbol is englishsentence.
semantics are perl5.  version is 1.004000.
default lex prefix is /\s+|\A/.
concatenate lines is q{ (scalar @_) ? (join "-", (grep { $_ } @_)) : undef; }.
default action is concatenate lines.

englishsentence: subject, verb, conjunction, object.

englishsentence: subject, verb, object.

specializernoun: noun.  q{ "specializernoun($_[0])" }.

ordinarynoun: noun.  q{ "ordinarynoun($_[0])" }.

subject: specializernoun, ordinarynoun.  q{ "spsub($_[0]+$_[1])" }.

subject: noun.  q{ "subject($_[0])" }.

noun: nounlex.

nounlex matches /fruit|banana|time|arrow|flies/.

verb: verblex.  q{ "verb($_[0])" }.

verblex matches /like|flies/.

object: preposition, noun.  q{ "ob(prep($_[0])+n($_[1]))" }.

conjunction: /like/.  q{ "conjunction($_[0])" }.

preposition: prepositionlex.

prepositionlex matches /a\b|an/.

';

my $data1='time like an arrow.';
my @values1=Parse::Marpa::mdl(\$grammar_description,\$data1);
for my $i(@values1) { say $$i; }

my $data2='time flies like an arrow.';
my @values2=Parse::Marpa::mdl(\$grammar_description,\$data2);
for my $i(@values2) { say $$i; }

Output:

subject(time)-verb(like)-ob(prep(an)+n(arrow))
subject(time)-verb(flies)-conjunction(like)-ob(prep(an)+n(arrow))
subject(time)-verb(flies)-conjunction(like)-ob(prep(an)+n(arrow))
subject(time)-verb(flies)-conjunction(like)-ob(prep(an)+n(arrow))
subject(time)-verb(flies)-conjunction(like)-ob(prep(an)+n(arrow))
spsub(specializernoun(time)+ordinarynoun(flies))-verb(like)-ob(prep(an)+n(arrow))
spsub(specializernoun(time)+ordinarynoun(flies))-verb(like)-ob(prep(an)+n(arrow))
spsub(specializernoun(time)+ordinarynoun(flies))-verb(like)-ob(prep(an)+n(arrow))
spsub(specializernoun(time)+ordinarynoun(flies))-verb(like)-ob(prep(an)+n(arrow))

PS: If I replace the conjunction-definition (conjunction: qr{like}. q{ "conjunction($_[0])" }.) with a terminal (conjunction matches /like/.), the quadruplication ceases and I get exactly one result for each of the two interpretations (but I lose the action on the conjunction).
Using

conjunction: conjunctionlex.  q{ "conjunction($_[0])" }.

conjunctionlex matches /like/.

I get the unwanted quadruplication back.