while (<DATA>) {
  my @accum;
  my $ate_the_whole_thing = 0;
  while (/\G$item_regex/g) {
    push @accum, [$1, $2, $3];
    $ate_the_whole_thing = (pos() == length);
  }
  if ($ate_the_whole_thing) {
    print join ',', @$_, "\n" for @accum;
  }
}

##</code><code>##

while (<DATA>) {
  my @accum;
  push @accum, [$1, $2, $3] while (/\G$item_regex(?=$item_regex*\Z)/g);
  print join ',', @$_, "\n" for @accum;
}