In-Portal uses a block concept to out data from database on a page.
So you basically define a block of HTML somewhere and then pass that block name to a tag, that will use it like in example below:
This will output all links in a current category using a "sample_element" block. However, there are tags, that require multiple blocks to passed in, e.g. "footer_render_as", "header_render_as" and so on.
If block content is a plain short text without HTML, then can simply use this approach to pass it without creating a new block:
<inp2:l_PrintList render_as="sample_element" footer_render_as="html:it's a footer"/>
So you need to pass "html:any_text_here" instead of a block name. You can also pass "html:" (will result in empty string).
Problem is that first char of passed text will be stripped off.
Ready for testing.