How do I add a dictionary like Rockyou?

[U_nix]

Think like that:

normal md5(pass): Create a md5 hash from a string.

md5crypt(pass): create a md5 from the md5 from the md5 ... till you have done it 1000 times.

edit:
This:
$P$
$1$
$x$

are just prefixes created like this:#
crypt($password,'$1$'.$hash.'$');

After that comes a salt and the md5 or just the md5.

If they use diferrent prefixes but the same hash algo it doesn` t matter if hashcat cuts both prefixes in one function.