Embperl is a Perl module, which allows one to embedded perl code into text files. In the beginning, HTML::Embperl allowed one to insert blocks of perl in an HTML file, similiar to ASP, JSP, PHP, and so forth. You could have a file that was all HTML, and be rendered like HTML is normally rendered. Blocks of code, starting with '[-' and ending with '-]' denoted perl code. This has great power, as a web designer can layout a page in Dreamweaver, Frontpage, or some other WIMP tool, then have a programmer insert the perl code to interact with a database.
Embperl even has syntaxes to read in other formats. So, it could be convinced to treat SSI ?, PHP, or other styles as Embperl code. This makes it easier to port a website from another templating or preprocessing system to Embperl.