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

$count_quotes = $string =~ tr/"/"/;

if($count_quotes && ($count_quotes % 2 != 0)){
  # there is an odd number of quotes in the string
  $quotedstringerror = 1; 
  # use this to show user an error message later
}elsif($count_quotes){
  # there is an even number of quotes in the string
  $quotedstrings = 1;
}

if($quotedstrings){
  @quotedstrings = $string =~ /"([^"]*?)"/g;
  # get them all out with m//
  $string =~ s/"[^"]*?"//g;
  # remove them from the original with s///
}

@unquotedstrings = split(/ +/,$string);

# grab remaining regular strings using split

print "\@quotedstrings: @quotedstrings \n";

print "\@unquotedstrings: @unquotedstrings \n";

# output: @quotedstrings: three five
#         @unquotedstrings: one two four six