hash1 has a key of name with values of uid,gid and gecos? uid,gid and gecos are accessed only through name, joe blow in this case

The bold portion is correct. The name's value is a reference to an anonymous hash, which has the keys of uid, gid, and gecos, who point to their respective values.

Every hash has key/value pairs; it's what the values contain--another hash, for instance--that make them powerful.

Here's another way to look at it: every time you see the curly braces with a name, think "key of"; so, $hash2{$name}{$uid} results in $hash2 with a key of $name, then the key of $name with a key of $uid, which yields the value of $uid.

Now, based off of this information, can you explain the 2nd hash again?

Update: A little rewording.