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

my $string = 'one "two three" four five "six seven eight" nine';

my @list = split /
 [ ]"            #opening quotes
 |               #or
 "[ ]            #closing quotes
 |
 [ ]             #a space
 (?!.*?\w")
     # that's not before any number of characters followed
     # by a closing quote (allows EOL at quote)
                 /x, $string;