The goal for this idea, as I understand it, is to write a GUI program which allows users to specify connections between components and then generates code to do it. There's no real need to create an intermediary specification language there, since it's so easy to do code generation with Perl. Seriously, it's so simple that beginners often use it too much, eval'ing as a solution to everything.
Of course, if people WANT to write the specification language by hand then you could use XML for it, or you could use some kind of simple macro language. If it was simple enough, you could use Template Toolkit for it. Regardless, I don't think you'll see non-programmers writing it by hand.
I don't think the HTML templating debate is really so similar. HTML with templating constructs usually is coded by hand, often by non-programmers, and it doesn't lend itself to the same kind of GUI tool approach that's described here because it's a mix of formatting and simple control structures that can't be fully shown with either a WYSIWYG approach or a flowchart approach (like XBeans seems to have). I generally prefer mini-languages like Template Toolkit over in-line Perl solutions when generating HTML because they make things easier on the HTML coders and help prevent pollution of templates with too much programming logic. These concerns don't really apply to an XBeans project.
