I had a bit of a problem when first encountering xor with more than two operands as well. It made sense after I thought about it linguistically instead of mathematically. When speaking people often use a string of "or"s to mean "pick one and only one of these choices, the the exclusion of all others".
Also I suspect that perl6's linguistic interpretation of "xor" (only one true item in list) will be more useful to programmers than a mathematical reductionist interpretation (odd number of true items in list). I think a note explaining the reasoning behind perl6's behavior on exclusive-or with >2 items ought to go in the synopsis, as it's bound to come up again.
