thank you ww
I do wish I knew how to copy error messages without having to write them down. I use strawberry perl, and the console gives the error message without an opportunity to copy it. I just assumed that if anyone ran the code they would get the same message.
it reads something like:
next_prime <n> : input '1.84467440869813e+019' must be a positive integer at c:\subdirectory... line 20