For one virutal includes just run the cgi-script and print the output so you can't specify a sub (well you could with some params, but that could get convulted). Secondly virtual includes are more for html files that don't have execute permission already, and are nice for including html templates (like a header file) for example, and will proably just cause a syntax error in a cgi script (will when testing over the command line at least). Require just includes the perl-script in a perl script so you could call the subs normally like they were in the same file.

You should look at Simple Module Tutorial for an even better way to include separate sub routines in multiple perl-scripts. Oh, Welcome to Perlmonks too :).

Now to your question.

I gather that you wish to create some dynamic web-pages. SSI is indeed one way to do so, but it is not the most flexible. As already said it will simply include the output of a script or file (which could be a Perl script or anything else which can be run in your webserver and provides output).

A much more useful, flexible and interesting way of making dynamic websites is by using a templating system such as The Template Toolkit (but there are many others) or by handcrafting your HTML through Perl and the CGI-module. Have a look at these and see how infinite the possibilities are for using Perl in the World Wide Web!

And of course the not-to-be-missed CGI-course of Ovid is a good start.

this is some raw info.. just to help out..

Subs are chunks of reusable code. By themselves they are little use other then as text in your html

scripts. programs, use subs to do stuff.

<!--#include virtual="cgi/cal.cgi"--> and then you get your calendar on the shtml page. You may want to play with passing parameters in the query string to that.