First off, what program is generating this logfile? Someone may have already written a parser for this type of logfile if it isn't a custom rolled application. Try searching CPAN for the module.

If it is a custom rolled app, then I would suggest writing an OO module that takes each line as a separate object, parses it and dumps it off to a function to handle each class/category of line and go from there. Aggregating the stats can become another part of the module.