[1] manakai makes use of some user data names (as used with getUserData and setUserData methods of Node interface) for its own purpose.

[2]
User Data Name Value Description
manakai_has_reference boolean Whatpm::HTML sets this user data to charset attribute of meta element, as a flag whether the attribute contains any character entity reference or not. This user data is referenced by Whatpm::ContentChecker::HTML for conformance checking of charset attribute.
manakai_di integer? Source document ID
manakai_pos Array reference of array reference of four Perl numbers List of line and column numbers in the value followed by line and column numbers in the source. (OBSOLETE)
manakai_source_column integer The column number in the line in the source file, from which the node has been created by the parser.
manakai_source_f Perl Path::Class The Path::Class object identifying the source file from which the node has been created by the parser. Typically used in the Document node.
manakai_source_file_name DOMString The path to the source file from which the node has been created by the parser.
manakai_source_line integer The line number in the source file, from which the node has been created by the parser.
manakai_sps sps data structure Source positions data structure for the node
manakai_title_metadata DOMString This user data can be specified for a Document. It represents the title metadata from a higher-level protocol. It is used to check the conformance of an HTML document with no title element.

User Data Name	Value	Description
`manakai_has_reference`	`boolean`	`Whatpm::HTML` sets this user data to `charset` attribute of `meta` element, as a flag whether the attribute contains any character entity reference or not. This user data is referenced by `Whatpm::ContentChecker::HTML` for conformance checking of `charset` attribute.
`manakai_di`	`integer?`	Source document ID
`manakai_pos`	Array reference of array reference of four Perl numbers	List of line and column numbers in the value followed by line and column numbers in the source. (OBSOLETE)
`manakai_source_column`	`integer`	The column number in the line in the source file, from which the node has been created by the parser.
`manakai_source_f`	Perl `Path::Class`	The `Path::Class` object identifying the source file from which the node has been created by the parser. Typically used in the `Document` node.
`manakai_source_file_name`	`DOMString`	The path to the source file from which the node has been created by the parser.
`manakai_source_line`	`integer`	The line number in the source file, from which the node has been created by the parser.
`manakai_sps`	sps data structure	Source positions data structure for the node
`manakai_title_metadata`	`DOMString`	This user data can be specified for a `Document`. It represents the title metadata from a higher-level protocol. It is used to check the conformance of an HTML document with no `title` element.