I played a bit with redo some time ago. It hit a chord with the way I like to do things (small, minimalistic tools that do one thing right). But it was hard to find my way around it, and for certain things (commands that produce more than one "product") the only answers were, in all honesty, hacks. Best example I remember now is bison, which produces a .c and a .h file. The hack was to produce a tar which contained the .c and .h files, declare that as the output from bison, and then have rules that state that your .c and your .h depend on the tar. Blergh.