personally.. I\'d do it like:

on *:input:#: {
if ($1 == !away) {
tnick $+($me,$chr(124),Away)
describe $chan I am currently away.
}
elseif ($1 == !back) {
tnick $mnick
describe $chan I\'m back.
}
elseif ($1 == !afk) {
tnick $chan $+($me,$chr(124),AFK)
describe I\'m currently AFK at the moment.
}
}

if you wanted to use it this way.

Reasons:

1. Using tnick instead of nick allows you to reference $mnick to get back to the default nick, whereas nick replaces $mnick. Also, using nick you would still have that nick if you were to disconnect and reconnect etc.
2. Describe $chan is the proper way to do actions to a channel from a script.
3. You dont have all the on inputs that you had as, I believe only the first one ever should have worked.
4. You dont have the bracket mismatches.