This logging framework is also minimalistic: no categories/hierarchiecal loggers, no custom levels, no config file, or other whistles and bells. And the interface & default levels are rather syslog-oriented. But it's fast alright. The POD doesn't mention a comparison to Log::Log4perl, but a casual benchmark shows that it's at least 10x faster.
So this module will certainly come handy if you have a performance critical application.
Btw, note that the benchmarks are done for actual logging to output. For log statements that do not actually get logged (e.g. because the level is below the desired output level), I don't find that extreme differences in overhead between logging frameworks. For example, on my Athlon64 X2 5600+ PC, Log::Fast's overhead is roughly around 3mils/sec, while Log::Log4perl is around 1,5mils/sec.