I'd characterize lib's use of unix conventions as unusual. Having environment variables with values suitable for a different operating system would be odd. It might be because of the source file, operating environment distinction though. lib's value is used at compile time and is directly in the source so it may be less copacetic to require a OS-neutral representation. The environment variable though is completely divorced from the perl script. In fact, it is applicable to all perl scripts so in that context I still hold that it would strange to require unix conventions in a very non-unix place.