Control structures include loops and tests, and they are normally inserted using hyperlinks with the py3o:// protocol.
In the current version of the py3o. template, two control structures exist: py3o://for="varname in iterable" and py3o://if="condition". Both need to be closed with py3o:///for and py3o:///if, respectively. Note that there is no else in a condition; you need to make a second py3o:// if blocked with the opposite condition.
Caution: There are two forward slashes in the opening hyperlink URL and three in the closing hyperlink URL.
With the constraint of using a hyperlink in mind, the result is very similar in spirit to the templating of emails explained in the Email Templates recipe earlier in the chapter.