TODO
----

 * have a deep look at Regexp::Common

 * Support "common" Regular Expressions for IP addresses, hostnames, etc.
   Should we "export" them via use Regexp::Log qw( :common ); ? 

 * a better fields() method, or a better way to work with fields added
   by _preprocess() and _postprocess()

 * add a concatenate() method that perform a join'|', @_, or
   call presuf() if Regex::PreSuf is present
