While

Here is a straightforward translation of the task description:

my $n = 1024; while $n > 0 { say $n; $n div= 2 }

The same thing with a C-style loop and a bitwise shift operator:

loop (my $n = 1024; $n > 0; $n +>= 1) { say $n }

And here's how you'd really write it, using a sequence operator that intuits the division for you:

.say for 1024, 512, 256 ... 1