======
proc ?append {v_name args} {
   upvar $v_name v
   if {![info exists v]} {
     return -code error "expected $v_name to exist!"
   }
   if {[array exists v]} {
     return -code error "can't set \"$v_name\": variable is array"
   }
   foreach val $args {
     append v $val
   }
   return $v
 } ;# GPS
======

[DKF]: I've updated the code above to match the calling convention for [append]

[MC]: I've updated the code to return the value of $val and to give the same error message if you try to append to the name of an array, like [append] does :-)

----
See also [?set], [?lappend]

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