Run expect script in systems that don't support it out of box

Noob question ..

My Java based application needs to change some user passwords based on some user actions. Since this application can run on Redhat AS2.1 / AS4.0 / Solaris 9 etc, the most safe and portable solution that I could think of was: Use expect.

Now, expect is not available on all platforms, and I don't want to install tcl / tk / expect to be able to run my application. So, what's the simplest way for me to achieve what I want to?

Keep a expect binary and required libraries in a local directory in the application? How can I do this? Any other ideas

Can anybody please suggest something ?