to method should accept 2nd parameter as 3rd argument to the called "callable"

[omitobi]

Line 65 of Piper should be changed from:

$result = $pipe(...$this->extraParameters[$key], ...[$result]);

$result = $pipe(...[$result], ...$this->extraParameters[$key]);

[omitobi]

This will break using piper(['a', 'b'])->to(array_map(...), strtoupper(...)) because function is called first for array_map.