The package is used in documentation files (that use the doc
package); with it the code listings will highlight (for
example) pairs of curly braces with matching colors. Other
delimiters like \if ... \fi, are highlighted, as are the names
of new commands. All this makes code a little more readable,
and helps during process of writing. Three options are
provided, including a non-color option designed for printing
(which numbers delimiters and underlines new commands).
