This works, though not in the same order, and like BrowserUK's solution does not work for embedded quotes. (TMTOWTDI).

use strict;
use warnings;

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

my (@quoted,@unquoted);

my $length = 0;
while ( $string =~ /\G\s*(?:("[^"]+")|([^"\s]+))(?:\s+)?/g  )
{
  if ( $1 ) { push @quoted,$1 }
  else { push @unquoted,$2 }
  $length = pos $string;
}

unless ( length($string) == $length ) { print "Quotes did not match" }
else  {
   local $\ ="\n";
   print q(@quoted:), join ",", @quoted;
   print q(@unquoted:),join ",",@unquoted;
}
[download]

And just for fun heres another solution:

use strict;
use warnings;

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

my (@quoted,@unquoted);

$\ ="\n";

1 while ( $string =~ s/"([^"]+)"/push @quoted,$1;''/ge );
if ( $string =~ /"/ ) { print q(A " was found so failure) and exit; }
push @unquoted, split " ", $string;

print q(@quoted:), join ",", @quoted;
print q(@unquoted:),join ",",@unquoted;
[download]

I doubt either solutions are the best solution. I think the best solution would depend on the strings and what you mean by a quoted string (can there be escaped quotes inside the string if so neither solution presented here will work). Well good luck, on your quest for knowledge.

-enlil