According to the Z-machine 1.1 standard:
2OP:1 1 je a b c d ?(label)
Jump if a is equal to any of the subsequent operands. (Thus @je a never jumps and @je a b jumps if a = b.)
je with just 1 operand is not permitted.
So what should be the result of
@je a? Should it crash/UB (as the last paragraph specifies), or be a no-op (as the paragraph above that specifies)?