Synopsis:
   on [<modes>]yell [<serial#>] [-|^]<match> { <action> }

Description:
   This is hooked by fairly useless but necessary in beta yell()s. They
   are present in the client for debugging purposes, and scripters may not
   want them to appear. ON ^yell will suppress their output.

Parameters:
   $0-    text of the yell()