I don't really understand what is your problem - but reading perldoc perldsc should help you.

And perhaps what can you help as well is playing with the code you posted:

$hash{key}[0]{email} = 'email@email';
$hash{key}[0]{timestamp} = time;
[download]

This sets the first element of the array to the hash  {email => 'email@email', timestamp => time} (the {array} in your example seems to be redundant). And to set the second element of the array:

$hash{key}[1]{email} = 'email@email';
$hash{key}[1]{timestamp} = time;
[download]