Declaring a new hash

my %desc;

This lets perl know that you plan on using a hash with the name desc.

Adding an element

$desc{"key1"} = "data for key 1"

Adds the value data for key 1 into the hash desc, with a key key1.

Iterating through a hash

Environment variables are passed to perl via the ENV hash. The example below lists all environment variables

foreach $key (sort keys %ENV) {
    print "$key = $ENV{$key}\n";
}