Originated by Tom Wilkason on comp.lang.tcl.

Modifications by [DGP].

  if {[package vcompare [package provide Tcl] 8.4] < 0} {
      proc tcl::K {a b} {return $a}
      proc lset {listName index val} {
          upvar $listName list
          set list [lreplace [tcl::K $list [set list {}]] $index $index $val]
      }
  } ;# end if