my $number_of_positions = 10;
my @positions = (1..200);
for my $i (1..$number_of_positions) {
    $arry[splice(@positions, rand(@positions), 1)] = 15;
}

##</code><code>##

my $number_of_positions = 10;
my @positions = (1..200);
map {$arry[splice(@positions, rand(@positions, 1)] = 15;} (1..$number_of_positions);