I would say, as a categorical statement, that you always want to find, and to use, a CPAN module of recent vintage to do these things.   Don’t pore through the module and cabbage code from it:   use the module exactly as it is.

Of course, we know that Microsoft is easy to deal with.   We know that they never create file-formats that are secretive or difficult to understand.   (Oh, no-o-o, they would never do such a thing!)   Therefore, when you find a CPAN contribution that has undertaken the chore of understanding that format ... that is the way that you should do it.

The same is true for output:   there are CPAN modules for tab-delimited text files, too.   Granted, tab-delimited is a comparatively trivial format to deal with, but not entirely.   IMHO, even a slight amount of hair-pulling to do such things is an unjustifiable abuse of precious follicles.

Actum Ne Agas:   “Do Not Do A Thing Already Done.”