Invoking tclsh or wish from Bourne Shell

Here is a template for a Bourne shell script I used that accomplishes the following:

Allows me to specify a specific version of Tcl and Tk to use (and assumes that the versions are identical).
Allows me to specify the paths to those different versions such that I insure I use those versions and not other versions that happen to reside on my system (Linux).
Sets the TCLLIBPATH environment variable to the directory or directories where extra packages are to be found. Currently set to "." which will have to be changed for your use.
Is able to be used for calling wish or tclsh.

Here is the script:

  #!/bin/sh
  # -*-mode: Shell-script; indent-tabs-mode: nil; -*-

  uname_s=`uname -s | sed 's,[. -],_,g'`
  uname_r=`uname -r`; uname_n=`uname -n`
  OS_REV=`echo ${uname_s}_${uname_r} | sed 's,[. -],_,g'`

  # Customize as needed:
  tcl_partial_version=8.4
  tcl_full_version=8.4.1
  # directory above the Tcl "bin" directory:
  tcl_head_dir=/scratch1/tcl${tcl_full_version}/$OS_REV
  # directory above the Tk "bin" directory:
  tk_head_dir=/scratch1/tk${tcl_full_version}/$OS_REV

  tcl_bin=$tcl_head_dir/bin
  tk_bin=$tk_head_dir/bin

  TCL_LIBRARY=$tcl_head_dir/lib; export TCL_LIBRARY
  TK_LIBRARY=$tk_head_dir/lib; export TK_LIBRARY

  if [ ! -d $TCL_LIBRARY ]; then
      echo "ERROR: TCL_LIBRARY of $TCL_LIBRARY does not exist as a directory"
      exit 1
  fi

  if [ ! -d $TK_LIBRARY ]; then
      echo "ERROR: TK_LIBRARY of $TK_LIBRARY does not exist as a directory"
      exit 1
  fi

  # echo TCL_LIBRARY $TCL_LIBRARY
  # echo TK_LIBRARY $TK_LIBRARY
  # echo TCLLIBPATH $TCLLIBPATH

  # I do not know if modifying the PATH is a good idea, but I did it just to be safe since on my system there
  # are multiple versions of Tcl and Tk executables in the PATH, and I want to be sure to be using a specific version:
  PATH="${tcl_bin}:${tk_bin}:$PATH"; export PATH

  # Customize as needed:
  # TCLLIBPATH must be set to the path of where our packages are, and
  # the pkg_mkIndex has to be called to create a file in that
  # directory all for the sake of being able to call "package require FooBar 1.0":
  TCLLIBPATH=.; export TCLLIBPATH

  # Call tclsh for just Tcl scripts:
  ### tclsh${tcl_partial_version} a_script_that_uses_FooBar.tcl "$@"

  # Call wish for just Wish scripts:
  wish${tcl_partial_version} a_script_that_uses_FooBar.tcl "$@"

RS: Note that since 8.4, it is no longer necessary to keep a separate wish - best always call tclsh, and start Tk-ish scripts with

 package require Tk