Nobody forces you to use any kind of shell with redo. Its .do files can be anything you want: ELF object files, shell scripts, Perl, Python, whatever, just make it executable and obey trivial simple rules (stdout and three arguments).
And again noone forces you to use multiple files too :-). You can literally have just single default.do file for the whole project. apenwarr/redo somewhere explicitly noted that. Separate .do files are only for convenience and ability to automatically depend on target's build rules independently from others, that Make just do not do at all.
