Off the top of my head but I think that should be backticks, not double quotes? So that `racecar` is read as a list of characters? I might try it later.

>> Prolog goes in order, and goes deep. This is notoriously problematic, because it's incomplete.

Yes, because it can get stuck in left-recursive loops. On the upside that makes it fast and light-weight in terms of memory use. Tabled execution with memoization (a.k.a. SLG-Resolution) avoids incompleteness but trades off time for space so you now risk running out of RAM. There's no perfect solution.

Welcome to classical AI. Note the motto over the threshold: "Soundness, completeness, efficiency: choose two".