I searched at CPAN, and found a couple of interesting modules:
* Net::YahooMessenger. This module seems to have issues with recent Yahoo! Protocol updates, because it consistently gave me the following error while trying to login.
Operation now in progress at Net/YahooMessenger.pm line 315.
* Net::YMSG. This module appears to have similar issues and gave me the following error:
Connection refused at Net/YMSG.pm
Perhaps I could sit down, follow the French Cafe Technique, and listen to the conversation between my Yahoo! Messenger Client and Servers to figure out their language.
Imagine you wanted to learn French, and there were no books, courses etc available to teach you. You might decide to learn by flying to France and sitting in a French Cafe and just listening to the conversations around you. You take copious notes on what the customers say to the waiter and what food arrives. That way you eventually learn the words for "bread", "coffee" etc.
But I'm not sure I have the required patience to do this today.