

          The following variables are set and/or used by the Tcl
          shell.

          argv A list containing the arguments passed in from the
               command line, excluding arguments used by the Tcl
               shell.  The first element is the first passed argument,
               not the program name.

          interactiveSession
               Set to 1 if Tcl shell is invoked interactively, or 0 if
               the Tcl shell is directly executing a script.  Normally
               checked by scripts so that they can function as a
               standalone application if specified on the command
               line, but merely load in and not execute if loaded
               during an interactive invocation of Tcl.

          noAutoExec
               If this variable exists and has a value of 1, then the
               Tcl shell will not attempt to exec an non-existent
               command as a shell command.

          programName
               The name that the Tcl shell is executing as.  All
               directory components are removed from the program name.

          TCLDEFAULT
               Name of the default file that was used to locate all
               other files used by the Tcl shell.

          TCLENV
               Array that contains information used internally by
               various Tcl procedures that are part of the Tcl shell.
               Entries that you might want to modify are defined here.
               Don't change any other entries.

          TCLENV(topLevelPromptHook)
               Contains code to run to generate the prompt used when
               interactively prompting for commands.  The code in this
               hook will be evaluated and the result will be used for
               the prompt.

          TCLENV(downLevelPromptHook)
               Contains code to run to generate the prompt used when
               interactively prompting for continuation of an
               incomplete command.  The code in this hook will be
               evaluated and the result will be used for the prompt

          TCLINIT
               The name of the file that initializes, and does startup
               processing of, Tcl.

          TCLPATH
               Path to search to locate Tcl scripts.  Used by the load
               and demand_load commands.  The path is a Tcl list (i.e.
               zero or more space-separated directory names).
