RPL equivalents to BREAK, CYCLE, EXIT, etc.?

[HP67]

Not to me, despite the technical correctness of your two points.

The first example used one fixed loop and one test. The counter-example used an indeterminate loop, an explicit counter variable, and two tests. That isn't simplicity nor clarity. Rather, I think Thomas motivated BREAK very well with his example. That is how it would be coded in any number of languages that don't impose a particular paradigm on the coder. The first version is simpler, clearer, more efficient, and less error-prone. The second version trades away clarity for a theoretical view of correctness that is not connected to an actual implementation. And the loop in the second example is actually a fixed-count loop in the degenerate case anyway, which weakens the argument that a definite loop structure is not appropriate.