Seeing the explanation of how the path coverage instrumentation that comes with #AFLplusplus works made me realize that it would actually be not just possible but even probably feasible to build something that's just "fully compatible" with what AFL expects to receive.

It's really just a large array of byte values, the address and size are supplied by AFL, where you increase a value at a position when a given edge has been traversed.

The number any given edge gets is just every relevant BB's number xor'd with the previously seen BB's number shifted by 1.

What number do you give a BB? Uniform random numbers seem to be good enough for a start!

An open question I have is that we do compile and then run some code at compile time when compiling #rakulang code, so ideally the "same" input code (for a suitable definition of same) would get the same numbers for all BBs so that only consequential changes in behavior are considered interesting by the fuzzer ...

@manwar Again, #RakuLang offers some #OneLiner solutions to the challenge:

Count Prefixes: ```
@array.map({$str.starts-with($_)}).sum
```

Valid Times: ```
([X~] .comb.map({ /\?/ ?? (0..9) !! $_})).grep(/^$<h>=[\d\d]\:$<m>=[\d\d]$ <?{ $<h> < 24 && $<m> < 60 }>/).elems
```

@manwar Again, #RakuLang offers some #OneLiner solutions to the challenge:

Alphabet Index Digit Sum: ```
( $str.trans(['a'..'z'] => [1..26]), *.comb.sum ... * )[$k]
```

Valid Token Counter: ```
.words.grep(/^ <:Ll>+ [ \- <:Ll>+ ]? <[,.!]>? $/).elems
```