In general, this either will Just Work, or else it won't work.

Whether it works or not depends. It depends on stuff. It potentially can depend, for instance, on what operating system you're using, what filesystem (e.g., on Windows it can matter whether it's FAT32 or NTFS, and of course it's never possible with FAT16), what hardware architecture (in particular, whether it's a 32-bit or 64-bit architecture), what compiler was used to compile your perl, what version of which set of C standard libraries it was compiled against and how they were configured when they were compiled, which compiler options were used, and assorted other arcane circumstances you may or may not have any control over.

I'm assuming here that the only problem is that the file is over 2GB. You *did* try your same code, with no changes at all, with a smaller-than-2GB file first, I assume, to make absolutely sure that the file size is the only problem. If not, do so forthwith. Otherwise, my next advice would be to try it on a different computer with a different perl and, if possible, a different operating system and filesystem. As a rule of thumb, it is somewhat more likely to work on more recent versions of perl, on more recent operating systems, and especially on 64-bit systems.