OpenBSD's carrying some local patches, Perl rand appears to be using the libc drand48(3) on OpenBSD, which uses arc4random_buf(3) internally, unless Perl srand is called, then it uses srand48_deterministic(3)? Not sure precisely as it's also using arc4random(3) directly to seed something.
This is slightly different from how it's handled outside the Perl software ecosystem, as all the srand* functions effectively became nops on OpenBSD in favour of strong random numbers, and userland ports had to be patched to use the deterministic variants if needed. I guess that would be hard with things like CPAN.
https://github.com/openbsd/src/commit/2e109fb9e8c0dc273648dd...
https://github.com/openbsd/src/commit/2e109fb9e8c0dc273648dd...
https://github.com/openbsd/src/commit/2e109fb9e8c0dc273648dd...
Looks like upstream Perl also uses drand48 from FreeBSD, with its own internal RNG. But I guess this can be overridden with build options.
I'd imagine something like pwgen would be better, but I doubt it matters here.