If you want a block of zeroes, then you may actually be looking for a PDL solution, in which case do:

use PDL;
$ndarray = zeroes($cols,$rows);
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If not, you can still do (albeit it's only somewhat efficient - most work is done in C and/or XS, not the interpreter):

use PDL;
$array_of_arrays = zeroes($cols,$rows)->unpdl;
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