my @a; ...
my $na; my $Na;
$na = $#a;
$Na = ( 0, 1..$na );
@a = ...;
for my $i (@Na)...

##</code><code>##

for my $i (0 .. $#a)

##</code><code>##

use strict;
use warnings;

my @a  = qw( / /home /var /tmp /var/tmp );
my @b;
$b[$_] = `ls $a[$_]` for (0 .. $#a);

for my $i (0 .. $#a)
{
    my @c = split("\n",  $b[$i]);
    printf("%s%s%s\n\n", $a[$i], ($i ? '/' : ''), $c[$_]) for (0 .. $#c);
}