Update: OP changed the question completely, so now my reply only makes limited sense.

Most of the perl monks who read your question are pretty good at Perl, but know next to nothing at about biology. So if you want helpful replies, you should explain what you mean with

Generate given Length random intervals from Genome data

in a way that doesn't require prior biology knowledge. And you also need to explain how that should lead to the expected output.

Also we don't know what length.pl does, so we can't even try to run your program.