Apache Guide: Advanced SSI Techniques Page 2
Any other variable (either ones that you define, or normal enviroment
variables) can be used in conditional statements. With Apache's ability to set
environment variables with the
SetEnvIf directives, and other
related directives, this functionality can let you do some pretty involved
dynamic stuff without ever resorting to CGI.
SSI is certainly not a replacement for CGI, or other technologies used for generating dynamic web pages. But it is certainly a great way to add small amounts of dynamic content to pages, without doing a lot of extra work.
See the docs on
mod_include for more information on using SSI.