That does something else then what the OP does. You're filtering out the undefined elements of @$aoa (that is, top level elements), while the OP wants to remove (according to his code), the undefined elements of the elements of @$aoa.

That is, if $aoa is 

[
  [2, undef, 4],
  [undef, undef, 5],
];

[download]
he wants to end with 
(2, 4, 5)

[download]
not with 
(2, undef, 4, undef, undef, 5)

[download]
which is what your code ends up with.

Note that you probably intended to write defined $_ instead of defined @$_.

In reply to Re^2: Flatten sparse AoA by JavaFan
in thread Flatten sparse AoA by FloydATC

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