Or you could use:

my @items = reverse unpack 'A'x(length $number), $number;
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which, from my benchmarking, is *slightly* faster, and probably more easily extended to splitting a string on variable-length segments. Say, for example, that you wanted to split your string into segments of length 3:

my @items = reverse unpack 'A3'x(length($number)/3), $number;
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Not that you asked about that, of course. :)