Why does this code with TCL Upvar command generate an error?

So I thought I understood how the TCL upvar command worked, but for some reason I cannot seem to trace why this code generates an error –

#!/usr/bin/env tclsh


proc run_check {} {
    set src dut.acore.B2.Vin
    set conlist1 [list dut.acore.B2.Vin dut.acore.N1__Bidir_2__ddiscrete_5.Aout dut.acore.DCORE.CLK]
    puts $conlist1

    set conlist2 [_lremove $conlist1 $src true]
    puts $conlist2
}


proc _lremove {listName val {byval false}} {

    upvar 1 $listName list
    puts $list


    #if {$byval} {
    #    set list [lsearch -all -inline -not $list $val]
    #} else {
    #    set list [lreplace $list $val $val]
    #}

    return $__list
}




######################################
##Run Command
######################################
puts [run_check]

On running this code, I get the following –

(base) ./remove.tcl 
dut.acore.B2.Vin dut.acore.N1__Bidir_2__ddiscrete_5.Aout dut.acore.DCORE.CLK
can't read "list": no such variable
while executing
"puts $list"
(procedure "_lremove" line 4)
invoked from within
"_lremove $conlist1 $src true"
(procedure "run_check" line 6)
invoked from within
"run_check"
invoked from within
"puts [run_check]"
(file "./remove.tcl" line 35)

Any thoughts on this ??

>Solution :

When you call _lremove you need to pass it the variable name conlist1 but you are passing its value. Change

set conlist2 [_lremove $conlist1 $src true]

to

set conlist2 [_lremove conlist1 $src true]