#!/usr/bin/perl -w
use strict;

my $input = '[S [NP This NP] [VP is [NP [NP the turning point NP] ' . 
	'[PP to [NP the left NP] PP] NP] VP] . S]';

$input =~ s/^\[S\s*(.*?)\s*S\]$/$1/;

my $bracket_count = 0;
my @output;
my $build_var;

foreach (split(//, $input)) {
	$build_var .= $_;

	if (/\[/) {
		$bracket_count++;
	} elsif (/\]/) {
		$bracket_count--;
	}

	if ($bracket_count == 0) {
		push @output, $build_var if ($build_var ne ' ');
		$build_var = '';
	}
}

foreach (@output) {
	print '"', $_, '"', "\n";
}