traversing (and accessing values in) a hash of hashes

[James marks]

Hello folks,
I'm wondering if any of you could help me with a code problem? I'm 
relatively new to Perl, coming to it from AppleScript, and I've written 
a Perl script that parses my server access_log and creates a hash of 
hashes that looks essentially like this:

192.168.1.1 =
                                $user_agent = "...GoogleBot..."
                                $user_type  = "robot"
192.168.1.3 =
                                $user_agent = "...Linux...Firefox..."
                                $user_type  = "human"
192.168.1.4 =
                                $user_agent = "...Yahoo! Slurp..."
                                $user_type  = "robot"
192.168.1.5 =
                                $user_agent = "...Windows...MSIE..."
                                $user_type  = "human"
etc...
So, in the first hash, the ip address is the key and the value is the 
second, nested hash.

I want to traverse that hash of hashes to extract the user agent of 
each IP whose user type is "robot" like this:

LIST OF ROBOTS VISITING SITE:
192.168.1.1 "...GoogleBot..."
192.168.1.4 "...Yahoo! Slurp..."
etc...
I've been struggling with various versions of a foreach loop but can't 
seem to get it to work. Is it possible to traverse a hash of hashes and 
extract data based on a value from a key/value pair that is nested in 
another hash?

I could just create two hashes, one for humans and one for robots, but 
one hash that contains all the information seemed to be a more elegant 
solution...

Any help would be greatly appreciated.
Thanks,
James