Unless one is doing it for fun, as an exercise, to check the validity of the list, or to expand a list, there's no reason to write a program that generates prime numbers starting from 2. We promote people to reuse code and not reinvent the wheel. There's no reason to be different when it comes to data.

I'm not so sure whether a sieve beats reading them from disk

Yep - a half-decent sieve does beat reading from disk ... unless it's a very short list that you're after.

Cheers,
Rob
Update: Actually ... come to think about it ... a half-decent sieve might beat reading from disk, even if it is a very short list

Ovid said:

This is part of a larger set of code which is intended to be pure Perl, ...

Can you write a "half descent sieve" in Perl?

Also, how about if you want the 2e6 through 3e6 primes the first time you call and the 1e6 through 2e6 the second time?

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