If you use Net::Telnet to localhost, login in as the new user, you can run commands via the telnet session and still process data as the real user.

One reason to do this is if sudo is missing and you are not allowed to install.

We have a network of machines and I maintain a central perl system on a NFS mount. The boxes on the network don't have sudo installed and to install would be frowned upon but they can run the central perl. I suppose I could sneak sudo onto the central perl directory structure.

Anyhow localhost doesn't expose to network and would provide a solution if sudo is unavailable.