The forward method passes control to another run mode and returns its
output. This is equivalent to calling '$self->$other_runmode', except that
CGI::Application's internal value of the current run mode is
updated.

This means that calling '$self->get_current_runmode' after calling
'forward' will return the name of the new run mode. This is useful for
modules that depend on the name of the current run mode such as
CGI::Application::Plugin::AnyTemplate.

For example, here's how to pass control to a run mode named 'other_action'
from 'start' while updating the value of 'current_run_mode':