This example illustrates difference of precedence by resolving of not fully-qualified namespace variables 
in procedure using [variable] and [global].

The test creates several nested namespaces and uses procedure `tv` acquiring the variable using supplied arguments, 
testing its access and finally output the access-method, the var-name and namespace where it is called from and the 
value of variable (or error if it unresolvable).

So `::P::C::tv global P::v` tries to access NFQ variable `P::v` from procedure of namespace `::P::C` using [global], 
whereas `::P::C::tv variable P::v` does the same using [variable].

The test calling it 4 times is repeated twice (without and with additional nested namespaces/variables).

======
variable v "::v"
namespace eval ::P {
  proc tv {h n} { puts -nonewline [format "%.4s %4s from %-7s ->   " $h $n [namespace current]]; catch { $h $n; set v } res; puts $res }
  variable v "[namespace current]::v";
  namespace eval C {
    variable v "[namespace current]::v";
    proc tv {h n} [info body ::P::tv]
  }
}
proc test {ns} {
  puts "  ================  test $ns   === "
  namespace eval $ns {
    tv global   P::v
    tv variable P::v
    tv global   v
    tv variable v
  }
}

puts "================== without ::P::P::v and ::P::C::P::v =================="
test ::P::C; test ::P

puts "================== create ::P::P::v and ::P::C::P::v =================="
foreach n {::P::C::P ::P::P} {
  namespace eval $n {  variable v "[namespace current]::v" }
}

test ::P::C; test ::P
======
results in:
======
================== without ::P::P::v and ::P::C::P::v ==================
  ================  test ::P::C   ===
glob P::v from ::P::C  ->   ::P::v
vari P::v from ::P::C  ->   can't define "P::v": parent namespace doesn't exist
glob    v from ::P::C  ->   ::v
vari    v from ::P::C  ->   ::P::C::v
  ================  test ::P   ===
glob P::v from ::P     ->   ::P::v
vari P::v from ::P     ->   can't define "P::v": parent namespace doesn't exist
glob    v from ::P     ->   ::v
vari    v from ::P     ->   ::P::v
================== create ::P::P::v and ::P::C::P::v ==================
  ================  test ::P::C   ===
glob P::v from ::P::C  ->   ::P::v
vari P::v from ::P::C  ->   ::P::C::P::v
glob    v from ::P::C  ->   ::v
vari    v from ::P::C  ->   ::P::C::v
  ================  test ::P   ===
glob P::v from ::P     ->   ::P::v
vari P::v from ::P     ->   ::P::P::v
glob    v from ::P     ->   ::v
vari    v from ::P     ->   ::P::v
======

** See Also **

   `[variable]`:   Declares and optionally [set%|%sets] variables in a [namespace].

   `[global]`:   Access global variables or variables in a [namespace].

   `[set]`:   Reads or assigns a value to a variable.
       
   `[namespace upvar]`:   Gives a variable in one namespace a name at the current [level].
       
   `[upvar]`:   Links a variable at some higher level to a variable at the current [level].

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