Authen::OTP is a One Time Password perl module implementing RFC 2289. It supports MD4, MD5, and SHA1. It goes beyond computing the nth OTP. It helps admins maintain users OTP passwords, authenticates users, updates their current states, provides the challenges, etc. It can also be used by clients to compute their Nth OTPs given a challenge.
Eventually I'll add POD and create the standard install style package for CPAN, but for now, feel free to download and manually place it where you want.