how to get elements outside the for loop

[Kush]

use strict;
use warnings;
use feature qw( say );

my @aa = ("A", "C", "D", "E", "F", "G", "H", "I", "K", "L", "M", "N", "P", "Q", "R", "S", "T", "V", "W", "Y");

my $pair;
for my $n1 (@aa) {
for my $n2 (@aa) {
$pair = $n1 . $n2;
}
}
my @codons=unpack( "(a2)*",$pa ir);
print @codons;

# these are the 20 amino acids and i have to make 400 possible combination of two

# amino acid(di amino acid) like this: AA AC AD ...... CA CC CD CE CF CG.....YA.....Y Y
#showing output only "YY"