my $s = ' one "two three" four five "six seven eight" nine';
my @w = $s =~ /
  \s* #strip whitespace outside of paren "blocks"
  (?:"(?{local $openq=1}))? #note fact of open-quote without storing
  ((??{$openq ? '[^"]*' : '\w+'})) #store block
  (?:(??{$openq ? '"' : '\b'})) #gobble up closeq or word-boundary(really nop in this case)
  /gx;
local $" = ':';
print "@w\n";