Edit: woop. My answer has nothing to do with your question. Funnay...

It looks like some MIPS dialect. In this case, remember that you have a 4 stage pipeline, and that any jump code will flush the two last stages. meaning that

set 00, r1ja L1set 00, r2  ; (1) this line is still in the pipeline and WILL BE EXECUTEDL1:

(1) is said to be in the "last delay slot". To avoid the execution of (1), put a nop right after the jump.

In your case, the beq (branch is equal) does the same. "set 00, r5" is in the LDS, and is executed.

Regards,