Selectively include/exclude pieces of text, allowing the user to define new, separately controlled, comment versions. All text between \comment ... \endcomment or \begin{comment} ... \end{comment} is discarded. The opening and closing commands should appear on a line of their own. No starting spaces, nothing after it. This environment should work with arbitrary amounts of comment, and the comment can be arbitrary text.

Other `comment' environments are defined by % and are selected/deselected with \includecomment{versiona} and \excludecoment{versionb} These environments are used as \versiona ... \endversiona or \begin{versiona} ... \end{versiona} with the opening and closing commands again on a line of their own. The author is Victor Eijkhout.