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[macro-replace]; replace arg2 with arg3 in arg1; NOTE: ARG2 and ARG3 *must*  be the same length!exten => s,1,SetVar(Repl_field=1)exten => s,2,Cut(Repl_new=ARG1,${ARG2},1)exten => s,3,SetVar(Repl_dst=${Repl_dst}${ARG3}${Repl_new})exten => s,4,SetVar(Repl_field=$[${Repl_field} + 1])exten => s,5,GotoIf($[${LEN(${Repl_dst})} <= ${LEN(${ARG1})}]?2)exten => s,6,SetVar(REPLACED=${Repl_new:1})