onTime {
  my $attr = $NODE->getAttr("something");
  my $val = $attr->getValue();
  my $was_updated = 0;
  foreach (@fixups) {
    $val += $_;
    $was_updated = 1;
  }
  @fixups = ();
  if ($was_updated) {
    $attr->setValue($val);
    $attr->doCallbacks();
  }
}