The random number generator does not need to be re-seeded, ever, in normal practice.

Every interpreter needs to be seeded. Perl will do that automatically, except when the interpreter is cloned by fork.

$ perl -e'
   rand(10);
   if (my $pid = fork()) { waitpid($pid, 0); }
   local ($,, $\) = (", ", "\n");
   print map int(rand(10)), 1..10;
'
8, 3, 9, 8, 8, 2, 3, 8, 4, 8
8, 3, 9, 8, 8, 2, 3, 8, 4, 8
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