Revision history for smartmatch

0.05  2012-06-23
      - add callback_at_level to get the coderef to call smartmatch recursively
        as though it were called at a given caller level

0.04-TRIAL  2012-06-23
      - restructure some internals for thread safety
      - add test demonstrating recursive smartmatch callbacks

0.03-TRIAL  2011-07-10
      - Add a hack to workaround perl RT#77468 on perls before 5.14

0.02-TRIAL  2011-07-10
      - Add a missing perl core function for < 5.14

0.01-TRIAL  2011-07-08
      - Initial release