To check if a domain is using cloudflare (perl code):

my $whoiscmd = "/usr/bin/whois";
sub uses_cloudflare_dns
{
    my $domain = shift;
    my $retval = system("$whoiscmd '$domain' |grep -i 'cloudflare' > /dev/null");
    return (($retval >> 8) == 0);
}

To check blacklists:

my $score = 0;
my $reason = "";
my $hostcmd = "/usr/bin/host";
sub check_blacklists
{
    my $ip = shift;
    # Do a sorbs lookup (determine if it is a dynamic ip)
    my ($a, $b, $c, $d) = split('\.', $ip);
    my $ret = `$hostcmd $d.$c.$b.$a.dul.dnsbl.sorbs.net|grep 'has address'|head -n 1`;
    if ($ret =~ /has address ([0-9\.]+)/)
    {
        if ($reason ne "")
        {
            $reason .= ", ";
        }
        $reason .= "your outgoing mail server is listed in SORBS";
        $score += 100;
        if ($debug eq "true")
        {
            print "mail server $ip listed in sorbs: 100 added to score (total score=$score)\n";
        }
    }

    # Do a spamhaus lookup
    $ret = `$hostcmd $d.$c.$b.$a.zen.spamhaus.org|grep 'has address'|head -n 1`;
    if ($ret =~ /has address ([0-9\.]+)/)
    {
        if ($reason ne "")
        {
            $reason .= ", ";
        }
        $reason .= "your outgoing mail server is listed in SPAMHAUS";
        $score += 100;
        if ($debug eq "true")
        {
            print "mail server listed in spamhaus: 100 added to score (total score=$score)\n";
        }
    }

    # Do a barracuda lookup
    $ret = `$hostcmd $d.$c.$b.$a.b.barracudacentral.org|grep 'has address'|head -n 1`;
    if ($ret =~ /has address ([0-9\.]+)/)
    {
        if ($reason ne "")
        {
            $reason .= ", ";
        }
        $reason .= "your outgoing mail server is listed in Barracuda";
        $score += 100;
        if ($debug eq "true")
        {
            print "mail server listed in barracuda: 100 added to score (total score=$score)\n";
        }
    }
}