I just needed to add an offset to a timing file, so used 1deval -expr 'a+9' -a stim.1D. It seemed completely logical to me. Unfortunately, 1deval only works on the first column, and the analysis run on 70+ subjects was all wrong.

It is perfectly clear in the documentation, and rather easy to test. It is totally my fault. But I think it would be a great idea to add a warning to 1deval whenever a user operates on a 1D file with multiple columns without explicitly stating which column they desire. This won't break anything, and might save a few users from a very annoying mistake that can be made early in a processing stream.