'''`[namespace] upvar`''', a subcommand of [namespace], makes a [variable] in a
[namespace] an alias for another variable.


** Synopsis **

    :   '''[namespace children]''' ''?namespace? ?pattern?''
    :   '''namespace upvar''' ''namespace otherVar myVar'' ?''otherVar myVar ...''?
    :   '''[namespace code]''' ''script''
    :   '''[namespace current]'''
    :   '''[namespace delete]''' ''?namespace namespace ...?''
** Description **
    :   '''[namespace ensemble]''' ''option ?arg ...?''
'''`[namespace] upvar`''' links ''otherVar'' to ''myVar'', after which any
operation on ''otherVar'' is identical to the same operation on ''myVar'', and
vice versa.  ''otherVar'' is resolved relative to ''namespace'', and my contain
[namespace%|%namespace qualifiers].  When `namespace upvar` is used in the
context of a namespace, ''myVar'' is resolved relative to the current
namespace, and always resolves to a namespace variable.  When `namespace upvar`
is used in the context of a procedure, ''myVar'' is resolved relative to the
current [stack frame], and resolves to a local variable in the current frame if
''myVar'' does not contain namespace qualifiers, or to some namespace variable
if it does.
    :   '''[namespace eval]''' ''namespace arg ?arg ...?''
`namespace upvar' is a convenience command that doesn't add any functionality
not previously available with `[upvar]`.  The following are equivalent:
    :   '''[namespace exists]''' ''namespace''
proc listns {{parentns ::}} {
set ns ::foo
upvar #0 ${ns}::bar boo

output:
and
======
% namespace eval ::test {set foo 1}
set ns ::foo
namespace upvar $ns bar boo

From 8.5 onwards, use this instead:
However, the second form is more efficient at the time the link is made, as it requires less string manipulation and parsing.
======

[DKF]: `namespace upvar` was created to help accelerate [Snit].
list the variables in a namespace:
======
list the procs in a namespace:
** See Also **
======
   [namespace]:   the primary command for working with namespaces
list the commands in a namespace:
<<categories>> Command | Tcl syntax help