use strict;
use warnings;

my @array = (1 .. 4);
while (@array) {
	my $first = shift @array;
	print "[$first]";
	push @array, $first / 2 if (!($first % 2));
}

##</code><code>##

[1][2][3][4][1][2][1]

##</code><code>##

use strict;
use warnings;

my @array = (1 .. 4);
for my $element (@array) {
	print "[$element]";
	push @array, $element / 2 if (!($element % 2));
}