www.yahoo.com isn't an IP. It's a name. Convert it to an IP first. For example, just changing "www.yahoo.com" to "216.109.118.67" made the script work here.

There are many ways to get perl to convert the name to a number - although in this case I just ran "host www.yahoo.com" at the command prompt. ;-)

(hint: I use Net::hostent)