What matija says about HTML::Template is true, in fact, any templating system will most likely fit the bill, personally, I like Petal, but that one has some Unicode bugs and XML quoting bugs, and requires your templates to be wellformed XML, which is most likely not what you want.

At the moment, I only see two special needs for templating, string interpolation and recursive macros.

For (intelligent) string interpolation, you will want to pass in any Perl scalar and have it automagically quoted correctly as a C string, in the same way that HTML::Template can automatically URL-encode or HTML-encode any scalar variable.

While the C macro preprocessor can also take some of the work, it might be useful for you to have recursive macro calls in your templating system, especially if you want to construct complex macros from smaller parts or move all OS logic out into separate templates instead of cluttering your output with huge nested blocks of #IFDEF.

I would start out with HTML::Template, code in the C-string-quoting function, and write the first generation templates in that. Then you will find out what additional functionality you need, and can move to the second incarnation.