Values assigned to identifiers can be text string, interger, floats, True/False booleans, or list. Several words are automatically considered as a list of words, so it is required to protect strings with spaces with quotes " " or ' '. Python triple quote notation is accepted to assign multiligne text. lines ending by "\" are continued to the next line.

Filter syntax is :
filter(value)
where value can be a string, list, ... or the result of another filter. For example, to get the last line of /var/log/httpd/access_log we may imagine that construction:

page.file.name = "access_log"
page.file.path = "/var/log/httpd"
page.data = html(last(splitlines(read(add(getvar(file.path) "/" getvar(file.name))))))

Most filters have a very simple design, and are defined in the dowww_filter.py file. It should quite easy to modify this file to adapt to your needs with basic python knowledge. (Some filters like Copy, Getvar and Plug are far more complex).