What operating system? Your kernel is reporting very large integers in the result of stat but some part of the system (either Perl or your C header files) think the inode number in the stat structure is supposed to be signed. ino_t is unsigned under both Solaris and Linux as far as I can tell, maybe you are using something else?

In any case, I think you can force the value to become unsigned without any worries because I don't think anyone has ever heard of negative inode numbers being valid. You found one way to do this: printf with a long integer specifier. I suggest XORing the value with 0. It's a noop but it forces the value to be treated as insigned:

no integer;   # you probably don't need this
              # just pointing out it doesn't work
              # under use integer;
$ino ^= 0;
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