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This is an excerpt from the latest version perlfaq4.pod, which
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4.10: Why aren't my random numbers random?

If you're using a version of Perl before 5.004, you must call "srand"
once at the start of your program to seed the random number generator.

BEGIN { srand() if $] < 5.004 }

5.004 and later automatically call "srand" at the beginning. Don't call
"srand" more than once--you make your numbers less random, rather than

Computers are good at being predictable and bad at being random (despite
appearances caused by bugs in your programs :-). see the random article
in the "Far More Than You Ever Wanted To Know" collection in
<>, courtesy of Tom
Phoenix, talks more about this. John von Neumann said, "Anyone who
attempts to generate random numbers by deterministic means is, of
course, living in a state of sin."

If you want numbers that are more random than "rand" with "srand"
provides, you should also check out the "Math::TrulyRandom" module from
CPAN. It uses the imperfections in your system's timer to generate
random numbers, but this takes quite a while. If you want a better
pseudorandom generator than comes with your operating system, look at
"Numerical Recipes in C" at <>.


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