reassigning values to variables question

[ToddAndMargo via perl6-users]

Hi All,

If I have a variable of type Buf which 10000000 bytes in it
and I find the five bytes I want, is it faster, slower,
or no difference in speed to overwrite the same variable
with the five bytes?  Or is it faster to put the five bytes
from the first variable into a second variable?

Many thanks,
-T