I was about to un-plug the old Linux work-horse (being slowly replaced by sexy Mac Mini Server) and realised that I hadn't converted my Currentcost Envi to work on OSX.
I initially thought it would be pretty straight-forward but after a labourious and unusual CPAN update to my perl installation I hit a road block with talking to the Prolific Serial to USB port.
After a few days of time here and there mucking around to get it to work, I discovered that the Mac uses serial ports differently to Linux. Essentially OSX maps a tty.usbserial port (dialin) AND a cu.usbserial port (dialout).
So a quick alteration to my routine to query the cu.usbserial port and everything now works perfectly. All weather and power data for merewether.com is now coming from the Mac Mini.