output

cf-agent -KIf ./set_array_values_with_list.cf 
R: Array: local_array[id1]=value
R: Array: local_array[id2]=value
R: Array: local_array[id3]=value

set_array_values_with_list.cf

body common control {

    inputs => { "../sketches/CFEngine/stdlib/cfengine_stdlib.cf" };
    bundlesequence  => { "main" };


}

bundle agent main
{
vars:
  "list" slist => {"id1", "id2", "id3"};
  "local_array[$(list)]"
    string => "value",
    policy => "free";

reports:
  cfengine::
    "Array: local_array[$(list)]=$(local_array[$(list)])";

}