I am not clear on what you are after. The title of your post says you want to access vi via teraterm which you are already doing apparently. What I gather is:

What you have:

• A minimal linux system
• A rs232 connection from a windows machine to the linux machine controlled by Teraterm

You want to run Perl scripts on the windows machine that will do things to the linux box.(?)

A quick look at Teraterm shows that there is no API available for it, thus no simple way to control Teraterm from Perl and thus straight forward way to pass things through Teraterm to the linux machine. Thus, Teraterm is unlikely to be part of your solution.

The only thing I can think of to try is to set up the rs232 connection as a network to get tcpip over rs232. Then I would use something like Net::SSH in my Perl scripts on the windows machine to automate whatever it is you want to accomplish on the linux machine. That assumes of course that the minimal linux machine is ssh capable.

It would be helpful to undestand a bit better what you want to do via this connection: Are you manipulating things on the linux box?..or are you just simply sending commands to it?...

Hope that is at least somewhat helpful...