I know two ways to achieve it. If you just want to store it, you may say:

push @sheet,[@array];
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or

$sheet[$n]=[@array];
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another way is to say:

push @sheet,\@array;
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or

$sheet[$n]=\@array;
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In the second way, when you change the values in @array, the corresponding value in @sheet will also be changed; but the first way wont.