Rather than relying on generic text substitution using m4 or perl or whatever, I suggest using SGML, the basis and common superset of HTML and XML, which comes with easy type checked text macro (entity) expansion for free or even type-aware parametric macro expansion. Where "type" refers to the regular content type of a markup element (ie. its allowed child elements and their expected order) but also considers expansion and escaping into attributes or other context such CDATA or RCDATA. Only SGML can extend to the case of properly expanding/escaping potentially malicious user comments with custom rules such as eg. allowing span-level markup but disallowing script elements, does markdown or other Wiki syntax expansion into HTML, can import external/syndicated HTML content, produce RSS and outlines for navigation, etc. Works well for nontrivial static site preparation tasks on the command-line; cf. linked tutorial and command line reference.

[1]: https://sgmljs.net/docs/producing-html-tutorial/producing-ht...

[2]: https://sgmljs.net/docs/sgmlproc-manual.html