Exactly what I was looking for, thank you!
I’m looking to mass search/replace phpbb [youtube] tags with actual youtube links from the phpbb importer, and this is a great first step.
PR for adding support for [youtube] tags.
https://github.com/dandv/discourse-post-process/pull/3
I’ve thrown a PR your way for dry-run option, too.
https://github.com/dandv/discourse-post-process/pull/2