a example of the script that doesn't work for every IRCd:

on *:TEXT:!regnick*:#: {
  /msg $chan $nick To register your nickname you must first be on that nickname then type /register password Email. For example I could type /register fingerfood myemail@myprovider.com 
  halt
}

For people who use Anope it's /ns register, and it's different for every other service package out there (some are in common however).

You can condense this in many ways using ethier by making it have some regex, or even making a list of if statements that use one on text event.