+ my $anded=shift;
+
+ if (! $anded || (($this || %{$this->[1]}) &&
+ ($other || %{$other->[1]}))) {
+ foreach my $influence (keys %{$other->[1]}) {
+ $this->[1]{$influence} |= $other->[1]{$influence};
+ }
+ }
+ else {
+ # influence blocker
+ $this->[1]={};