I am running an old version of Xitami. It does not have SSI support built in, so it uses some type of fake perl script to work with SSI. Works well. I don't know if it's been changed, but I think you do need Perl.
You need to change your thinking on locally viewing files if you are going to use SSI. What you are doing now, is opening up the files in your browser.
When you install a web server like Xitami, you are creating your own internet in your computer. You don't open files. What you do is connect to Xitami like you would connect to a web site. In the URL box, you would type 127.0.0.1 (the local address of your computer). If Xitami is setup and running, you will see the Xitami welcome screen. Then you can go in setup Xitami to point to the location of your web files. Then you use it like you are connected to a very fast internet site.