Practical Programming in Tcl & Tk, Third Edition

Namespace Variables

The variable command defines a variable inside a namespace. It is like the set command because it can define a value for the variable. You can declare several namespace variables with one variable command. The general form is:

variable name ?value? ?name value? ...

If you have an array, do not assign a value in the variable command. Instead, use regular Tcl commands after you declare the variable. You can put any commands inside a namespace block:

namespace eval foo {
    variable arr
    array set arr {name value name2 value2}
}

A namespace variable is similar to a global variable because it is outside the scope of any procedures. Procedures use the variable command or qualified names to reference namespace variables. For example, ...