perldoc -q hostname tells us:

       How do I find out my hostname/domainname/IP address?

       The normal way to find your own hostname is to call the `hostna
+me` program.  
While sometimes expedient, this has some problems, such as not knowing
+ whether you've got the 
canonical name or not.  It's one of those tradeoffs of convenience ver
+sus portability.

       The Sys::Hostname module (part of the standard perl distributio
+n) will give you the hostname 
after which you can find out the IP address (assuming you have working
+ DNS) 
with a gethostbyname() call.

           use Socket;
           use Sys::Hostname;
           my $host = hostname();
           my $addr = inet_ntoa(scalar gethostbyname($host || 'localho
+st'));
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Cheers,
Darren :)