my $x = 1;
my $y = 20;
my $looptimes = 10;

my %numbers = ();

foreach(1 .. $looptimes) {
    my $candidate = -1;

    do {
        $candidate = int(rand ($y - $x + 1)) + $x;
    } while(exists $numbers{$candidate});

    $numbers{$candidate} = 1;
}

say join ",", keys %numbers;