$ cat A; echo '* * * * *'; cat B
apple
cherry
carrot
lime
* * * * *
lime
orange
banana

##</code><code>##

$ perl -e 'open F,$ARGV[0] or die;shift;my %set = map {$_ => 1 } <>; for (<F>) {print if $set{$_}};' A B
lime

##</code><code>##

$ perl -e 'open F,$ARGV[0] or die;shift;my %set = map {$_ => 1 } <>; for (<F>) {print unless $set{$_}};' A B
apple
cherry
carrot

##</code><code>##

$ cat C
grape
apricot
cherry

$ perl -e 'open F,$ARGV[0] or die;shift;my %set = map {$_ => 1 } <>; for (<F>) {print unless $set{$_}};' A B C
apple
carrot

$ perl -e 'open F,$ARGV[0] or die;shift;my %set = map {$_ => 1 } <>; for (<F>) {print if $set{$_}};' A B C
cherry
lime