use List::Compare;
use strict;
open (F, "a.txt")||die("a.txt File cannot open\n");
open (S, "b.txt")||die("b.txt File cannot open\n");
my @a=<F>;
my @b=<S>;
my $lcma = List::Compare->new(\@a, \@b);
print $lcma->get_complement ,"\n"; # extra present in the second array 
print $lcma->get_unique ,"\n"; # extra present in the First array