Sorry I have trouble understanding all of this, that's why I gave a generic hint

The example code you showed seems to slide over a fixed array, but when dealing with huge files you need a dynamic approach.

Otherwise you wouldn't get the file into memory.

Unless there is "lazy" magic connected to the array via tie*, but this must be in other parts of the module, which I never used

In short, I'm confused what the question is and how to help.

*) Yep seems so https://metacpan.org/pod/List::Gen#generators