To my mind, you just need to memorize that arrays and hashes can contain only scalars and references, and in order to use contents of an object by its reference you need ->.

For example, 

#!/usr/bin/perl
use feature "say";

# This is an array of array references:
my @array = ( # "(...)" means array
 [ 1, 2, 3 ], # "[...]" means array reference
 [ 4, 5, 6 ],
);
say $array[1]->[2]; # 6
# firstly, we get the second element from the array
# secondly, it's a reference to an array, so we add "->" and get the t
+hird element of it

# this is a reference to an array of references of arrays
my $reference = [
 [ 7, 8, 9 ],
 [ 10, 11, 12 ],
];
say $reference->[0]->[1]; # 8

# this is an array of hash references
my @hashes = (
 { one => 1, two => 2, three => 3 }, # "{...}" means hash reference
 { one => 11, two => 22, three => 33 },
);
say $hashes[1]->{one}; # 11

[download]
You may also want to use Data::Dumper to look inside your data structures. Perl debugger (perl -d) command "x" is also useful.

Sorry if my advice was wrong.

In reply to Re: Concept map of data types by aitap
in thread Concept map of data types by programmer.perl

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