I'm not sure about what you want to do ! "+10" is not correct.
Replace "in" by "norm" and you'll see that the output is different than 0.
You can us jit.op @op @val 10, if you want to add 10 to each value in the matrix.
take another look. On my machine both expressions(in+10 and @op + @val 10) give a correct (non-zero) output with the 9999 element matrix, not with the 10000 element one. however SOMETIMES the expr version sometimes returns the correct output which makes me think there is actually a bug here...