Usage: ON [#|+|-|^|&|@]SILENCE [-|^]<parameters> [action]
  This is activated whenever you receive a SILENCE message from a server
  you are on.  The parameters for the action are as follows:
    $0    a plus ('+') if a SILENCE entry was added, or a ('-') if one
          was removed
    $1    the pattern silenced or unsilenced
