use Parse::RecDescent;
use Data::Dumper;

$::RD_AUTOACTION = q { [@item] };


$grammar = q{
start: seq

seq: '(' seqstr(s) ')'

seqstr: seq | tagstr

tagstr: OZN ( seq | rijec )

OZN: /[A-Z.,?'*:`*]+ /
rijec: /[\w-?,:<*`*]+/
};

my $parser=Parse::RecDescent->new($grammar);
my $result = $parser->start("(SBARQ (WHNP (WP Who))(SQ (VP (VBZ says)(, ,)(S (SBAR (`` ``)(IN If)(S (NP (PRP you))(VP (VBP do)(RB n<t)(VP (VB look)(ADJP (JJ good)))))(, ,)(S (NP (PRP we))(VP (VBP do)(RB n<t)(VP (VB look)(ADJP (JJ good)('' <<)))))))))(? ?))");
print Dumper($result);

##</code><code>##

use Grammar::BNF;
use Parse::RecDescent;
use Data::Dumper;


$::RD_AUTOACTION = q { [@item] };


my $g = Grammar::BNF.generate(Q:to<END>
<start> ::= <seq>

<seq> ::= '(' <seqstr(s)> ')'

<seqstr> ::= <seq> | <tagstr>

<tagstr> ::= <OZN> '(' <seq> | <rijec> ')'

<OZN> ::= /[A-Z.,?'*:`*]+ /
<rijec> ::= /[\w-?,:<*`*]+/
END
);

my $parser=Parse::RecDescent->new($g);
my $result = $parser->start("(SBARQ (WHNP (WP Who))(SQ (VP (VBZ says)(, ,)(S (SBAR (`` ``)(IN If)(S (NP (PRP you))(VP (VBP do)(RB n<t)(VP (VB look)(ADJP (JJ good)))))(, ,)(S (NP (PRP we))(VP (VBP do)(RB n<t)(VP (VB look)(ADJP (JJ good)('' <<)))))))))(? ?))");
print Dumper($result);