[Richard Suchenwirth] 2007-05-08 - The functionality of [take] is to retrieve the value from a variable, which is then [unset]. This is very simple, as you'll immediately see, but can be useful - I needed it for the global textvariable of a dialog. As the variable was named like the dialog window, which in turn had a name constructed with [clock clicks], the global variables causes pollution of ::. By using [take] when returning the result, the variable is now immediately unset.
 proc take _var {
    upvar 1 $_var var
    return [set var][unset var]
 }

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[Category example]