roslisp has a hierarchical logging system similar to roscpp.

(ros-info (topic subtopic) "X is currently ~a" x)

This prints a message at level info (the levels are debug, info, warn, error, and fatal) on the given topic and subtopic.

If the above was being run in node foo, at a shell do:

$ rosparam set foo/roslisp/topic/level warn
$ rosparam set foo/roslisp/topic/subtopic/level info

This would cause the above message to be printed (since the subtopic will print messages at or above level info).

The parameters are read at startup. They can also be reloaded during the node's execution by calling the foo/reset_debug_levels service.