# 20 random integers, 0-99
my @orig_list = map { int rand 100 } 0 .. 20;
my @selected = ();   # items selected
my $desired = 10;    # how many items to select
my %found = ();      # indexes already used
while ( scalar @selected < $desired ) {
    my $index;
    $index = int rand @orig_list until ! $found{$index}++;
    push @selected, $orig_list[$index];
}