http://www.purl.org/tcl/home/man/tcl8.4/TclCmd/tclvars.htm collects the
formal reference info for tclvars...


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The variables tcl_wordchars and tcl_nonwordchars define what
letters are treated as valid for words.  The variables are auto-loaded
along with the commands they control, such as [tcl_endOfWord].

This means that to change the characters that are valid, you must first
do something like:

        catch {tcl_endOfWord}

After this, you can then do something like:
    # We want the same behaviour on Windows as on Unix for double-clicking
    set tcl_wordchars {[a-zA-Z0-9_]}
    set tcl_nonwordchars {[^a-zA-Z0-9_]}

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   * [argc] - number of arguments the script was called with
   * [argv] - list arguments the script was called with

Unlike C, the argv does not include the name of the application itself
among the argument list.

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See also "[Tcl syntax help]" and "[magic names]".

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