The ``=pod'' directive does nothing beyond telling the compiler to lay off of through the next ``=cut''. It's useful for adding another paragraph to the doc if you're mixing up code and pod a lot.
Head1 and head2 produce first and second level headings, with the text on the same paragraph as ``=headn'' forming the heading description.
Item, over, and back require a little more explanation: Over starts a section specifically for the generation of a list using =item commands. At the end of your list, use =back to end it. You will probably want to give ``4'' as the number to =over, as some formatters will use this for indention. This should probably be a default. Note also that there are some basic rules to using =item: don't use them outside of an =over/=back block, use at least one inside an =over/=back block, you don't _have_ to include the =back if the list just runs off the document, and perhaps most importantly, keep the items consistent: either use ``=item *'' for all of them, to produce bullets, or use ``=item 1.'', ``=item 2.'', etc., to produce numbered lists, or use ``=item foo'', ``=item bar'', etc., i.e., things that looks nothing like bullets or numbers. If you start with bullets or numbers, stick with them, as many formatters you the first =item type to decide how to format the list.
And don't forget, when using any command, that that command lasts up until the end of the paragraph, not the line. Hence in the examples below, you can see the blank lines after each command to end it's paragraph.
Some examples of lists include:
That's it. The intent is simplicity, not power. I wanted paragraphs to look like paragraphs (block format), so that they stand out visually, and so that I could run them through fmt easily to reformat them (that's F7 in my version of vi). I wanted the translator (and not me) to worry about whether " or ' is a left quote or a right quote within filled text, and I wanted it to leave the quotes alone dammit in verbatim mode, so I could slurp in a working program, shift it over 4 spaces, and have it print out, er, verbatim. And presumably in a constant width font.
In particular, you can leave things like this verbatim in your text:
Doubtless a few other commands or sequences will need to be added along the way, but I've gotten along surprisingly well with just these.
Note that I'm not at all claiming this to be sufficient for producing a book. I'm just trying to make an idiot-proof common source for nroff, TeX, and other markup languages, as used for online documentation. Translators exist for pod2man (that's for nroff(1) and troff(1)), pod2html, pod2latex, and pod2fm.
If you had not had that blank line there, then the translators wouldn't have seen it.