A package for treating parts of one variable as a whole other variable. More description to come later, but the basic idea (via some of the tests) is:

 test list.stackLevels-1.1 {
    Passing the name of a child into a proc to be upvar'd\
        will still modify the parent
 } -setup {
    reset main child
 } -body {
    proc modify {&var} {
        upvar 1 ${&var} var
        set var [string toupper $var]
    }
    set main {a b {c d} e}
    shadow child main 2
    modify child
    set main
 } -result {a b {C D} e}

 test array.stackLevels-1.1 {
    Pass the child into a proc, and change it via upvar
 } -setup {
    reset main child
 } -body {
    proc modify {&var} {
        upvar 1 ${&var} var
        foreach {key value} [array get var] {
            set var($key) [expr {$value * 20}]
        }
    }
    array set main {a 1 b 2 c 3}
    shadow child main
    modify child
    getArraySorted main
 } -result {a 20 b 40 c 60}