gistfile1.txt

#!/usr/bin/env perl
use strict;
use Array::Diff;
use Data::Dumper;

my ($old, $new) = @ARGV;
open my $io, '<', $old;
my @old = <$io>;
chomp @old;
close $io;
open my $io, '<', $new;
my @new = <$io>;
chomp @new;
close $io;

my $diff = Array::Diff->diff(\@old, \@new);
print Dumper $diff;