Your mileage may vary: cav. [from the standard disclaimer
attached to EPA mileage ratings by American car manufacturers] 1. A
ritual warning often found in Unix freeware distributions.
Translates roughly as "Hey, I tried to write this portably, but who
_knows_ what'll happen on your system?" 2. More generally, a
qualifier attached to advice. "I find that sending flowers works
well, but your mileage may vary."