As stated earlier, you should include fully qualified DNS names or hostnames in URL masks whenever possible.
Excelerator resolves DNS names to their respective IP addresses and uses those addresses when pinning objects.
You can use this fact when constructing your pin list entries.
For example, if you use the DNS name www.foo.gov as the URL mask and you know that the DNS name foo.gov resolves to the same IP address, you don't need to include foo.gov in the pin list.
Excelerator will treat objects for both DNS names the same because both URLs resolve to the same IP address.
On the other hand, if www.foo.gov and foo.gov resolve to different IP addresses, separate pin list entries would be required to cover both sites.