com­ment – Selec­tively in­clude/ex­cludes por­tions of text

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 and 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.