Hey Frosty, I can tell you one thing for sure - it wasn't Machholz you saw. The comet is still in Eridanus and will be moving quickly down towards the Pleiades. Sorry mate!
It may have been a satellite though. What time did you see it? How bright was it? Was it a smooth motion? More details please
Just checked out
heavens-above and found two satellites within the vicinity of Sirius at your location of Melbourne:
Satellite 1 info
Satellite 2 info
The first one passed by Sirius at around 11pm-ish and the second one passed by (a bit further out) at around 11:30pm-ish. What you saw could be one of those
Most likely it was the first satellite link. Hope that helps anyhow.