SWPERRLEV
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  Function : Get child process return code

  Syntax   : niValue = SWPERRLEV()

  Return   : Child program return code

  This function returns the exit code of the child process. The exit code
  returned is the exit code of the last process which terminated prior to
  the command interpreter returning to the swap kernel. In the case that
  the command interpreter was the only process executed, the return code
  will be that of the command interpreter.

  Example  :
  SWPRUNCMD("Compile myprog -m",0,"","")
  IF SWPERRLEV() <> 0
      ? "Compile failed..."
  ELSE
      SWPRUNCMD("BLINKER @LINK.LNK",0,"","")
  ENDIF