osx man page for global

global(n)						       Tcl Built-In Commands							 global(n)

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NAME
       global - Access global variables

SYNOPSIS
       global varname ?varname ...?
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DESCRIPTION
       This command has no effect unless executed in the context of a proc body.  If the global command is executed in the context of a proc body,
       it creates local variables linked to the corresponding global variables (though these linked variables, like those created  by  upvar,  are
       not included in the list returned by info locals).

       If  varname  contains  namespace qualifiers, the local variable's name is the unqualified name of the global variable, as determined by the
       namespace tail command.

       varname is always treated as the name of a variable, not an array element.  An error is returned if the name looks like an  array  element,
       such as a(b).

EXAMPLES
       This procedure sets the namespace variable ::a::x
	      proc reset {} {
		  global a::x
		  set x 0
	      }

       This  procedure	accumulates the strings passed to it in a global buffer, separated by newlines.  It is useful for situations when you want
       to build a message piece-by-piece (as if with puts) but send that full message in a single piece (e.g. over a connection opened with socket
       or as part of a counted HTTP response).
	      proc accum {string} {
		  global accumulator
		  append accumulator $string 

	      }

SEE ALSO
       namespace(n), upvar(n), variable(n)

KEYWORDS
       global, namespace, procedure, variable

Tcl																	 global(n)