use List::Util;

sub unique_random_list {
    my ($from, $to, $count) = @_;

    $count = List::Util::min ($count, $to - $from);

    my @result;
    my @queue = [ $from, $to - $from, $count ];

    while (my $job = shift @queue) {
        my ($from, $length, $count) = @$job;

        if ($count == $length) {
            push @result, $from .. $from + $length;
        } elsif ($count == 1) {
            push @result, $from + int rand $length;
        } else {
            my $split_length = int ($length / 2);
            my $split_count  = List::Util::min (int rand $count, $split_length);

            my $pad_length = $length - $split_length;
            my $pad_count = $count - $split_count;

            $split_count += $pad_count - $pad_length
              if $pad_count > $pad_length;

            unshift @queue, grep $_->[2],
              [ $from, $split_length, $split_count ],
              [ $from + $split_length, $length - $split_length, $count - $split_count ];
        }
    }

    @result;
}

my @list = unique_random_list (10, 100, 30);