latex-dev: how to use?

[AW]

Hi!

This is a »do-it-for-me-pleeaaase» kind of question.

I'd like to test the development version of pdflatex and lualatex, see here: 
https://tex.stackexchange.com/q/506646/4736

The article by Frank Mittelbach (here: https://tug.org/members/TUGboat/tb41-2/
tb128mitt-quovadis.pdf) was to interesting to resist, but after investigating 
about how to implement the necessary commands in AUCTeX, I got stuck in 
commands like 

 Name: LaTeX
            Command: %`%l%(mode)%' %T

Ahem, whut? This is from customization of TeX-command-list. 

The trick seems to change the command from 'pdflatex ...' to pdflatex-dev 
...', but it would take much time for me to figure it out. 

Maybe for a reader of this list it is an easy exercise to provide the lisp 
code to make it possible to write on a per file basis 

% Local Variables:
% TeX-engine: luatex-dev
% End:

or 

% Local Variables:
% TeX-engine: pdftex-dev
% End:

and the file is compiled with lualatex-dev or pdflatex-dev?


Thank you!

Regards,

Alexander