[squid-users] blocking all non-domains

Since my users generally have no reason to be at a site w/o a domain name
(and most of those sites are ads/porn) I'm trying to block out all
dstdomain that match a IP address. I tried the following:

         acl numeric_block dstdom_regex \d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}

But the connection went through. Any thoughts on this from the general
populace?

-- 
Till Later,
Jake