I do realize looping and other logic are not allowed inside here docs so i'll need to rethink that

For your next implementation, perhaps think of using a full blown templating solution, such as Template::Toolkit which allows the logic to reside (partially) inside the template.

I had a similar problem and solved it by having the Perl script extract the data from the data sources, out it in a standard format (data structure) and then have Template::Toolkit-templates turn it into the required output-formats. Now, every time I need to have a new output format, I just have to write a new template and do not have to write a new script.

Alternatively, have a look at XML::Code which allows easy writing of XML-code or XML::Generator which is a bit more involved but has more possibilities. Both modules will take care of escaping "forbidden" characters.

Update: How could I forget XML::Writer? This venerable module has everything, but is not easy to use and I find it overkill for some more simple tasks. However YMMV.