proc main {} {
set mainBuff [struct::stack]

listMod mainBuff
}

proc listMod {bufArg} {
upvar $bufArg bufRet
set srvLstCon [getList]

foreach lin [lindex $srvLstCon] {
 $bufRet::push $lin <-- can't read "bufRet::push": no such variable
 }

return
}