#!/usr/bin/perl --
use Parse::RecDescent;
use Data::Dumper;
#~ $::RD_TRACE = 1;
$::RD_AUTOACTION = q { [@item] };

#~ (SBARQ 
#~     (WHNP 
#~         (WP What)
#~     )
#~     (SQ 
#~         (VBZ is)
#~         (NP 
#~             (NNP Head)
#~             (NNP Start)
#~         )
#~     )
#~     (. ?)
#~ )
my $grammar= q {

start   :seq(s)

## seq	: '('TAG (seq | word) | ("." "?")')'
## seq	: '(' TAG ( seq | word ) |  TAIL ')'

## seqWord: seq | word 
## seq	: '(' TAG  seqWord TAIL ')'
## seq: '(' TAG ( seq | word ) TAIL ')'
## seq     : '(' TAG ( seq(s) | word |  TAIL ) ')'
#~ seq     : '(' TAG ( seq(s) | word ) |  TAIL ')'
#~ seq     : opener TAG ( seq(s) | word ) | TAIL closer
#~ seq     : opener TAG ( seq(s) | word ) TAIL? closer
#~ seq     : opener TAG ( seq(s) | word ) TAIL closer
## seq     : opener TAG seqtween TAIL(?) closer
## seq     : '(' TAG seqtween TAIL(?) ')'
seq     : opener TAG seqtween TAIL(?) closer
seqtween: seq(s) | word 
opener : '(' 
closer: ')'
TAG     : /[A-Z]+/
TAIL    : "(. ?)"

word   : m(\w*)

 
};

$grammar = q{
start   : seq(s)
seq     : opener TAG sub_seq  TAIL(?) closer
sub_seq : seq(s) | word 
opener  : '(' 
closer  : ')'
TAG     : /[A-Z]+/
TAIL    : "(. ?)"
word    : m(\w*)

};
my $parser=Parse::RecDescent->new($grammar);

my $result = $parser->start("(SBARQ (WHNP (WP What))(SQ (VBZ is)(NP (NNP Head)(NNP Start)))(. ?))");
print Dumper($result);