Otherwise, if a Lit script contains escaped substitutions (like %%p in this test), they are unescaped during recursive application of substitutions, and the results are unexpected.
We solve it using the fact that double percent signs are first replaced with #_MARKER_#, and only after all the other substitutions have been applied, #_MARKER_# is replaced with a single percent sign. The only change is that instead of replacing #_MARKER_# at each recursion step, we replace it once after the last recursion step.