eReg is a program designed to help sysops deal with unregistered users.
The program itself is called like so:
  ereg &&nn &&mm &&Ax=???????? &&filename
	 ^    ^    ^	 ^	    ^
	 |    |    |	 |	    \	A filename to display for a 'warning'
	 |    |    |	 |		and more information
	 |    |    |	 \-----------{	The flags that indicate registered users
	 |    |    \-----------------{	Which access flags to use (A1-A4)
	 |    \----------------------{	Absolute maximum number of times a
	 |				user can log on before not being
	 |				allowed in the system
	 \---------------------------{	Number of logons before a user gets the
					'warning' file displayed to him.

Ereg is set up that if a user is past 'mm' logons, he will be presented
with three options: Register, get more info, or logoff.
Logging off kicks him off the board.
Choosing register will move the user to a menu called ereg. You can either
place your registration here, or just use an autoexecuting Mgoto to move
him to another menu, or the registration procedures of you choosing.
Choosing Get more info will display the filename specified in the ereg's
opt data.

As an example:
  ereg &&10 &&15 &&A4=------.. &&board.txt

  will show the file 'board.txt' to any user who has A4=------..
  and will give any user with a4=------.. the 3 options above.