This expression is actually equivalent to C<$x & ($y == 0)>, due to the
higher precedence of C<==>. This is probably not what you want. (If you
really meant to write this, disable the warning, or, better, write
-C<$x & ($y == 0 ? 1 : 0)>).
+C<$x & ($y == 0 ? 1 : 0)>). (This warning might also be produced when you
+use the bitwise exclusive or, C<^>. Consider using the low-precedence
+C<xor> operator instead. See L<perlop>.)
=item Possible unintended interpolation of %s in string