use strict;
use warnings;

open my $fh, '<', 'hosts' or die;
my @hosts = <$fh>;
close $fh;

my @new_hosts = grep { !/$ARGV[0]/ } @hosts;

print "\nnew_hosts:\n";
print join "", @new_hosts;

##</code><code>##

use strict;
use warnings;

open my $fh, '<', 'hosts' or die;
my @hosts = <$fh>;
close $fh;

print "Excluding these lines:\n";
my @new_hosts = grep { print $_ if /$ARGV[0]/; !/$ARGV[0]/} @hosts;

print "\nThe new array:\n";
print join "", @new_hosts;