Look at what is generated by Test::Inline. It creates a variable for STDOUT and STDERR, and captures all output there. I have used this approach to check for error messages, proper output, menus, etc.

Just looked at this module again (it has been a while since I have refreshed my copy), and I am not certain that it still does this the same way as was done in 0.15 (wow - time to refresh). See specifically $_STDOUT_ and $_STDERR_ variables.