I am leaning towards YAML for this.

Just a general note.  During my last job (in a lab mostly frequented by psychologists, linguists, etc.) I wrote a suite of modules for EEG/ERP analysis, and my general conclusion was that if you make the user interface too complex (as is unfortunately sometimes required for generic solutions), people simply aren't going to use the tool — in particular, if the entry threshold is high, and it doesn't come with lots of ready to use cut-n-paste examples.

In other words, using YAML would be fine if they know it already, but otherwise they might not be willing to learn it  (which could mean - at least if you work in the same lab - you'll always be the one eventually writing the code for them :)

I agree with your points and at the same time I am being realistic. I dont expect anybody from my work here to use this module - they all use statistical packages. I would expect the average Perl user though to be able to use it easily. My plan, is/was to have a separate tool and have something like "Cut and paste the column names in this space" and the markup would be generated automagically.

Thank you all for your useful comments. Spiros

Dealing with 150 fields is always going to be tedious. Whether you spread it horizontally over a single line, or vertically over 150 lines.

The nice thing about the prefix/suffix idea, is that it can be embedded in a standard Xsv file and normal Xsv handling can still be used. If the processor uses the header line, the fields just carry some extra information. If it discards ths headers, it just gets discarded. If it uses the field names for processing, you only need preprocess the first line to strip the suffixes to allow it to still work.

Things that a YAML/XML/Other format description would never allow.