Seeing all the halts, which aren't really needed, you might as well use goto if you fancy them:

away {
  goto $iif($1-,x,y) 
  :x
  if (!$away) { 
    tnick $me $+ $(|) $+ $$?="Please enter an Addon for your nick (away/sleep/brb):"
    msg $active [Away] I am now away. Reason: $1- - Time: $time(hh:nn:sstt)
    away $1-
  }
  else echo -a [Away] Error: You are already away - To return, just type: /away 
  halt
  :y
  nick $mnick
  msg $active [Away] I have returned from: $awaymsg ( $+ $duration($awaytime) $+ )
  away
  halt
}