syphilis wonders how one can override a system build-in sub, here is how to override rand() with your own algorithm or calling external module

Thank you for that.
I had come close ... but still managed to miss the correct incantation I was looking for.
I had done:

BEGIN {
  *CORE::GLOBAL::srand = \&my_srand;
  *CORE::GLOBAL::rand  = \&my_rand;
};
[download]

but failed to declare my_rand() and my_srand() inside the BEGIN{} block.
Not a very intelligent mistake to make ... but then, that's the nature of mistakes ;-)

I don't see a need for named subs anyway, and I think it looks more natural to use anonymous subs as you have done.
Here's a working version of what I was trying to come up with, by using named subs.

use warnings;
use strict;

BEGIN {
  *CORE::GLOBAL::srand = \&my_srand;
  *CORE::GLOBAL::rand  = \&my_rand;

  sub my_srand {
    use Win32::API;
    my $srand = Win32::API::More->new(
      'msvcrt', 'void srand(unsigned int seed)'
    ) or die "Error: ".Win32::FormatMessage(Win32::GetLastError());
    $srand->Call($_[0]);
  }

  sub my_rand {
    my $rand = Win32::API::More->new(
      'msvcrt', 'int rand()'
    ) or die "Error: ".Win32::FormatMessage(Win32::GetLastError());
    return int(($rand->Call()) * $_[0] / 32767);
  }
}

srand(0);
print int(rand(99)) for 0..9;

__END__

Outputs 023647263525973192
[download]

(However, I personally prefer the use of Inline::C, rather than Win32::API.)

Cheers,
Rob