Have you looked at the various examples for IPC::Open3? What you need to do, IIUC, is "simulate expect". After you do open3 on the command, go into a loop listening for output, then you must run a regex on the output and respond by printing "y\n" to the *HIS_IN filehandle.

Look at examples for running bc at example for ipc::open3

There are always little complications that can set in, like buffering, whether your $cmd behaves normally...some apps don't work well with IPC, unless you do some extra work, like with "top", which continually outputs.

You may be better off picking the brains of "all the monks", post your question again, with exact details of what you need to do.