/DEBUG[=debug-file]
  /NODEBUG            (default)

  Determines whether you run a TPU debug file to test procedures for
  an application you are creating.  TPU compiles, and executes the
  debug file---before executing TPU$INIT_PROCEDURE.

  Using /DEBUG without specifying a debug file runs the default TPU
  debugger---TPU$DEBUG.TPU, which provides commands to manipulate
  variables and to control program execution.  To start editing the
  code in the file you are debugging, use the GO command.  For more
  information about the debugger, read the comments in the
  TPU$DEBUG.TPU source file in SYSSHARE, or see the VSI Text Processing
  Utility Reference Manual or use the online help in EVE as follows:

     Command:  HELP TPU Debugger

  There are two ways to specify a debug file of your own:

  o  Define the TPU$DEBUG logical name to specify the debug file, and
     then use EDIT/TPU/DEBUG.

     Defining the logical name does NOT by itself run the debugger when
     you invoke TPU.  It only specifies which debug file is run when
     you use /DEBUG.  You can put the definition in your LOGIN.COM
     file.

  o  Use /DEBUG= and specify the debug file on the command line.

     For example, the following command edits a file named MYPROCS.TPU,
     using a debug file named MYDEBUG.TPU:

        $ EDIT/TPU myprocs.tpu /DEBUG=mydebug

  TPU assumes the debug file is in SYSSHARE.  If your debug file is
  stored elsewhere, specify the device (disk) and directory of that
  file.  You cannot use wildcards to specify the debug file.  You can
  use only one debug file at a time.  Default file type is .TPU.