I assume you've read the documentation and found nothing specifying any ordering. Which usually means there is none

Even if someone told you now that he knows that File::Find internally sorted the files alphabetically, would that help you in any way? Because you couldn't depend on that "feature". After the next minor update of the module this might not be the case anymore. Stick to what the module documentation says and not says.

Also the information text about the "preprocess" option hints strongly that whatever ordering the files may have, they are not ordered alphabetically or numerically. But obviously you could use that option to sort the names in any order you want