Perlfunc / sort:
    The comparison function is required to behave. If it returns
    inconsistent results (sometimes saying $x[1] is less than $x[2]
    and sometimes saying the opposite, for example) the results are
    not well-defined.
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I guess that means you don't really know what your code will give you. (Which kind of seems to be the point of it, but in another way. :))