#!/usr/bin/perl

use Data::Dumper;

my %line;
$why = "";
$a = A;
$b = B;
$c = C;

$line{$a}{$b}{$c} = 1;
print Dumper(\%line);

$i = 1;

for $a (keys %line) {
for $b (keys %{$line{$a}}) {
for $c (keys %{$line{$a}{$b}}) {

print "$a $b $c\n";

}
}
}
<p>It prints output : A B C