#!/usr/bin/perl -w
use warnings;
use strict;
my %topHash;

# (1) Perl automatically creates the hash table entries as needed
# (2) The undef value will be treated as zero, so the result of this
#     statement is that $topHash{77}{15}{Feb} is 1
++$topHash{77}{15}{Feb};

for my $k1 (keys %topHash) {
  for my $k2 (keys %{$topHash{$k1}}) {
    for my $k3 (keys %{$topHash{$k1}{$k2}}) {
      print "$k1 / $k2 / $k3 : '$topHash{$k1}{$k2}{$k3}\n";
    }
  }
}