logger is a [tcllib] package which attempts to improve on the [log] package by providing a configurable, hierarchical approach to logging, meaning that one can have not only levels such as critical, error and warn, but also 'services', such as irc, mime, or whatever one wishes to specify.  These services can also have a tree-like structure, so that you could have 'sub' services which are all also configurable via the root of that tree.  Furthermore, the code attempts to minimize impact on performance when logging is turned off for a particular service.  If all the stops are pulled out, it approaches the speed of not having the logging code at all.