The example given is probably the closest to evaluating a string as a series of operations on parameters passed to a function. So say evaluate('p0 * p1 + p2', p0, p1, p2). The proper evaluation of arithmetic expressions is quite hard but a recurring theme no matter what language you work with, so it would make sense to abstract that out and do it once and (hopefully) well.
The 'orders' are then the operators.
Keep in mind that this was written well before high level languages were common and that such subroutines were handcrafted pieces of code likely operating on a series of fixed memory locations rather than parameters passed on the stack.
A bit like you would do this in BASIC before structured versions of basic came along, set a bunch of global variables, GOSUB, read back the result from some other global variable.
This sort of arrangement made composition a very interesting and sometimes maddening affair.
Another way to read that fragment is as the beginnings of a high level interpreted language, I think that is given extra weight because of the debug possibilities and the fact that the program 'retains control'.