sort out program virtual domains from common log file for Webalizer

I followed the suggestion to use only one log file for all my virtual domains. Before I run webalizer for each virtual domain I sorted out the virtual domain, which worked fine when the traffic is low and the amount of log entry is low. Now I have some domains with and without a country ending and now I need a better way to sort it out. I would like to use a perl (?) program that sort out the domains into a /tmp/logfile.$virtualdomain instead of running the sort out every time. Maybe something like that exist, or anybody has experience to sort out this data. bye Ronald