what about reverse pack("f", 440.0)

Update1:
The reason for the difference on MAC and PC is that the real numbers are in the native machine format only. For more information see perldoc -f pack and perldoc perlport.

Update2:
sorry, my first idea works just with unpack("H*", reverse pack("f", 440.0)) vs unpack("H*", pack("f", 440.0))

By the way on my PC pack("f", 440.0) is 00 00 DC 43.
and pack("N", unpack("l", pack("f", 440.0))) just returns 43 dc 00 00

And the fastest solution would be a XS implementation.