while (pos($tag) < length($tag)) {
    if (m{ \G (\w+) \s* = }gcx) {
      push @args [ $1 ];
    } elsif (m{ \G (\w+) (?= \s* | \z ) \s* }gcx) {
      push @args, $1;
    } elsif (m{ \G (['"]) ( \\. | [^\\] )*? \1 \s* }gcx) {
      (my $quoted = $2) =~ s/\\(.)/$1/g;
      push @args, $quoted;
    } else {
      die "parsing error\n";
    }
  }
  for (my $i = 0; $i < @args; ++$i) {
    $args[$i][1] = splice(@args, $i + 1, 1) if ref $args[$_];
  }