my @population = (1..10); # destructive source
my $n = 3; # desired selection size
my @selection; # result appears here
while (@selection < $n) {
  my $swapper = int rand @population;
  push @selection, $population[$swapper];
  if ($swapper < $#population) {
    $population[$swapper] = $population[-1];
  }
  pop @population;
}