my @two_d = (
    [(undef) x 5],
    [(undef) x 5],
    [(undef) x 5],
    [(undef) x 5],
    [(undef) x 5],
);
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or

my @two_d;
push @two_d, [(undef) x 5] for 1 .. 5;
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It's tempting to try the x 5 trick a second time to fill the top level, but that gets you five references to the same row.

Replace (undef) with (0) if that's what you prefer.