What I often do, instead of having to guess, is run an "autoexpect" session. This will record your subsequent login/logout session and save it as an Expect script which can then be run to repeat the process. From there, converting it to Perl is trivial.

I have to note that - annoyingly - "autoexpect" is no longer included in the standard Expect package in my favorite Linux distro (Ubuntu); you need to 1) download the "expect-dev" package, and 2) ungzip and "chmod +x " the 'autoexpect.gz' found there. No idea why they did this... but I'm glad it's still available.