The regular arrays allow you to access elements by their index numbers, starting at 0.
Associative arrays allow you to access elements by key names. 
An associative array or hash holds a set of key/value pairs. 
A key name is any arbitrary scalar value.
Perl uses a percent sign (%) to indicate that a variable is a hash.
Any value in a hash can be accessed through its key name with the following syntax:
The dollar sign ($) means that the value held in the hash under a given key name is a scalar value.


$hash{keyname}