@list1only = grep { $presence{$_} == 1 } keys %presence;
@list2only = grep { $presence{$_} == 2 } keys %presence;
@list3only = grep { $presence{$_} == 4 } keys %presence;
@lists1and2only = grep { $presence{$_} == 1+2 } keys %presence;
@inall = grep { $presence{$_} == 1+2+4 } keys %presence;
# etc