I've come across much the same conundra in C. However, in the case of C, there was one instance that was platform dependent. It involved subscripts. Here is the snippet if I remember it correctly:

array[i++] = array[i++] + i;
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I actually found this in a piece of application code. Horrid, isn't it.

What would the perl equivalent do? I guess it would be consistent across platforms, since perl evaluates expressions in the same order on all platforms.