Hi guys, thanks for reviewing!
"Guarded logging" is a pretty standard practice, see for example: http://www.slf4j.org/faq.html#logging_performance, which also mentions that the overhead incurred is insignificant while at the same time making sure that potentially costly operations needed to construct the logged message are avoided when unnecessary.  Also, I'm using the % operator because the message *will* be generated per the guarded condition.

Note, to be more clear, this standard practice actually applies in general to both statically typed and dynamic languages but that do not have a "parameters by name" or similar mechanism, like in Scala, for example.