From language/operators

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Short-circuit exclusive-or. Returns the true argument if there is one (and only one). Returns the last argument if all arguments are false. Returns Nil when more than one argument is true.

This operator short-circuits in the sense that it does not evaluate any arguments after a 2nd true result.

say 0 ^^ 42;                             # OUTPUT: «42␤» 
say '' ^^ 0;                             # OUTPUT: «0␤» 
say 0 ^^ 42 ^^ 1 ^^ die "never called";  # OUTPUT: «Nil␤»

Note that the semantics of this operator may not be what you assume: infix ^^ flips to the first true value it finds and then flips to Nil forever after the second, no matter how many more true values there are. (In other words, it has "find the one true value" semantics, not "Boolean parity" semantics.)