"You are not declaring your loop variables. That practically guarantees that you don't use strict.pm."

How do you know that he didn't declare his loop variables? also what made you believe that he didn't use strict? His code could be something like this:

use strict;
use warnings;

my $i;
my @a = (1,2,3);

for $i (@a) {
    print $i;
}
[download]

The real point here is that, it is always a better idea to have the smallest possible scope for your variables, so it is nicer to code like this:

use strict;
use warnings;

my @a = (1,2,3);

for my $i (@a) {
    print $i;
}
[download]