Your problem is that for each generation, you create an array that for each child, holds the number of children it gets in the next generation.

There's no need for that. Far easier is:

my $people = ...;  # First generation.
my $generations = ...;
for (2 .. $generations) {
    $people += int rand 6 for 1 .. $people;
}
[download]

It can be made faster (by using a formula to calculate the number of children in each generation without the inner loop), but the above is simple, and most of all, won't run out of memory (assuming there's a few Mb available to start perl).

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