# full path to hosts file
use constant HOSTS_FILE => '/home/csssec/audit/css_hosts.txt';

# full path to local host binary
use constant HOST_BIN => '/usr/bin/host';

...

1;

##</code><code>##

#!/usr/bin/perl -w

use strict;

use Audit::Config;
use Check::DNSCheck;

# for every host in the hosts file
open(FILE, HOSTS_FILE) || die("$!\n");
while (<FILE>) {

        chomp($_);
        my $host = $_;

        next if ($host =~ /^(\s*)#/);

        my $chk = new DNSCheck($host);
        $chk->run();

}
close(FILE);

##</code><code>##

package DNSCheck;

use Audit::Config;
use strict;

sub new
{
        my $class = shift;
        my $host = shift;

        my $this =
        {
                host   => $host,
        };
        bless ($this, $class);

}

sub run
{
        my $this = shift;

        my $cmd = HOST_BIN . " $this->{'host'} 2>/dev/null";

        my $r = `$cmd`;
        if ($r !~ /has address/)
        {
                return(0);
        }

        return(1);

}

1;

##</code><code>##

Bareword "HOST_BIN" not allowed while "strict subs" in use at Check/DNSCheck.pm line 30.
Compilation failed in require at ./audit.pl line 6.
BEGIN failed--compilation aborted at ./audit.pl line 6.