/set can do math operations natively with two operands and one operator (math and bitwise logic.)
That's faster and handy, I'd like to suggest a switch for /set so that the full line is a $calc parameter.
set -sc %a 2+3 -5 * 8,%b a + b,%c,%d % $+ a,%e %d + 1
* set %a to -35
* set %b to 0
* set %c to
* set %d to -35
* set %e to 0
The assignment is not to be evaluated twice with the math occuring after, %e should be trying to $calc the plaintext "%a" string resulting in 0, %e shouldn't result in -34
