I think you're looking for

*ON::Ar = $HugeArrayRef
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The way it works is that it sets *ON::Ar{ARRAY} to be $HugeArrayRef. Thus $HugeArrayRef is now de facto the array that @ON::Ar represents. There's more about this in perldata (see e.g. "Typeglobs and Filehandles") and perlref for *foo{THING}.

lodin