use feature qw/say/;
my @bb = 1..10; 
while(my ($ind, $val) = each @bb){
	say "ind is $ind";
       	if($ind >5){
				while(my ($inner_ind, $inner_val) = each @bb){
		       	say "inner ind is $inner_ind, inner val is $inner_val"
		}
	}
}

# will endless loop since while share one iterator

while(my ($ind, $val) = each @bb){
	say "ind is $ind";
}
# this will quit loop successfully.