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

my @Month_Data;
# $Month_Data[0] is January's data $month_data[11] is December's
$Month_Data[0]=0;
$Month_Data[1]=5;

print "\nFrom an array\n";
print "January : ", defined $Month_Data[0]  ? $Month_Data[0] : 0, " widgets\n";
print "February: ", defined $Month_Data[1]  ? $Month_Data[1] : 0, " widgets\n";
print "December: ", defined $Month_Data[11] ? $Month_Data[11] : 0, " widgets\n";


# with names
print "\nFrom synchronised arrays with names\n";
my @Month_Names=qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec);

for my $i (0..$#Month_Names) {
    print "$Month_Names[$i]: " , defined $Month_Data[$i] ? $Month_Data[$i] : 0, " widgets\n";
}

# A structure (Array of Arrays)
my @Structure;

foreach my $Month (qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec)) {
    push @Structure, [$Month, 0]
}

print "\nFrom an array of arrays, we zero initialised these so no need to check defined\n";

foreach my $Month_Data (@Structure) {
    print "$Month_Data->[0]: $Month_Data->[1] widgets\n";
}

# Finaly a hash, order is lost but lookup by month is easy
my %Month_Records;
foreach my $Month (qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec)) {
    $Month_Records{$Month}=0
}

print "\nFrom a hash, order is lost\n";
foreach my $Month (keys %Month_Records) {
    print "$Month: $Month_Records{$Month} widgets\n";
}

print "\nBut lookup by any random month is easy\n";
print "July: $Month_Records{Jul} widgets\n";
__END__
From an array
January : 0 widgets
February: 5 widgets
December: 0 widgets

From synchronised arrays with names
Jan: 0 widgets
Feb: 5 widgets
Mar: 0 widgets
Apr: 0 widgets
May: 0 widgets
Jun: 0 widgets
Jul: 0 widgets
Aug: 0 widgets
Sep: 0 widgets
Oct: 0 widgets
Nov: 0 widgets
Dec: 0 widgets

From an array of arrays, we know all these are zero initialised
Jan: 0 widgets
Feb: 0 widgets
Mar: 0 widgets
Apr: 0 widgets
May: 0 widgets
Jun: 0 widgets
Jul: 0 widgets
Aug: 0 widgets
Sep: 0 widgets
Oct: 0 widgets
Nov: 0 widgets
Dec: 0 widgets

From a hash, order is lost
Mar: 0 widgets
Nov: 0 widgets
Apr: 0 widgets
Oct: 0 widgets
May: 0 widgets
Sep: 0 widgets
Jan: 0 widgets
Jul: 0 widgets
Dec: 0 widgets
Feb: 0 widgets
Jun: 0 widgets
Aug: 0 widgets

But lookup by any random month is easy
July: 0 widgets