#/perl/usr/bin
use warnings;
use strict;

my %line;

my $why = "";
my $key_a = 'A';
my $key_b = 'B';
my $key_c = 'C';

$line{$key_a}{$key_b}{$key_c}; # this is line 12

my $i = 1;

for my $loop_key_a (keys %line) {
	for my $loop_key_b (keys %{$line{$loop_key_a}}) {
		for my $loop_key_c (keys %{$line{$loop_key_a}{$loop_key_b}}) {
			print "$loop_key_a $loop_key_b $loop_key_c\n";
		}
	}
}