I bet that if the number 64 may change, the number of "15 element arrays" will also change. What you need is an array of array (references).

my @newarray;
while (my @array = splice @oldarray,0,15) {
    push @newarray,\@array;
}
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You wind up with an array "@newarray" in which each element contains a reference to an array of at most 15 elements.

Hope this helps.

Liz