We've already seen how a page can include a variable in the
input and have this be inserted into the output.
There is a special kind of per-page variable, using read_file, which sets
the value of a variable to the contents of the named file:
title: File Reading
src: read_file( file.wgn )
sidebar: read_file( sidebar.inc )
----
..
As a helper if you use "read_file( SELF )", then "SELF" will be
replaced with the page being read.
As an alternative to naming a part of your template, and expanding the content
within it you can of course use the HTML::Template file inclusion construct:
<!-- tmpl_include name='path.inc' -->
The inclusion path is relative to the directory containing the file being processed.