To include a preformatted, never-to-be-fiddled-with text (e.g. a code block) finish the prior paragraph with "::". The preformatted block finishes when the text falls back to the same indentation level as a paragraph prior to the preformatted block.
An example:
Whitespace, newlines, blank lines, and all kinds of markup
(like *this* or \this) is preserved by literal blocks.
Lookie here, I've dropped the indentation level
(but not far enough)
no more example
If a paragraph consists of only of "::", then it's removed from the output:
:: This is preformatted text, and the last "::" paragraph is removed
This is preformatted text, and the last "::" paragraph is removed
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