Fast Primes

[SMcNeill]

The _OrElse isn't an error.  It's just a case of you needing to upgrade your version of QB64PE.

No, can't be! I have the latest version (I always use the latest version):

I'd suggest trying another download and extract to a fresh directory.  13.1 definitely has _OrElse in it, and it should definitely NOT be white for you.  (It should be the same color as all the rest of your keywords.)

If a fresh download doesn't fix the glitch, then we'll want to know what OS/version you downloaded and are using, and we'll need to look into what the heck is going on.  The simple fact that nobody else has mentioned it not working, however, leads me to believe that your version is corrupted, or out of date, or pathing wrong, or some other add issue.