I suspect that migrating to Template::Toolkit would be significant amount of work, given how many templates/pages I'd have to handle, and also upating the loop-structures which currently get passed to HTML::Template.

Text::Xslate looks interesting, thanks for the link. If the compatibility is 100%, or near to it, then it might make sense to examine it.

For the moment I've written a simple perl script, (what else?), to take each of my page-snippets and the global layout file and just build a complete "layout+content" file for each one. That solves my immediate problem, and means I keep the benefit of one easy-to-update layout template.

Although I'm largely the person responsible for the site others do contribute at times, and it would be nice to avoid adding extra hurdles to that process.