The migration document will never be "perfect". It cannot cover all the cases people have incorrectly used (mis)-features of Dancer 1 (see how I used request->referer), just as the documentation of Dancer will never be perfect.
Just slap a "known issues in the migration process" at the top of the pod and when someone complains that some case was not covered,
congratulate for being the first to encounter the issue ask politely for a pull request.
I am sure the license already say that this software is provided "as is" without any implied liability
and I don't think everything needs to be automated.