Scalar found where operator expected at ./BP_Chap11_Exer1.pl line 30, near "]$j"

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              print $chessboard[$i]$j];

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syntax error at ./BP_Chap11_Exer1.pl line 19, near "$_}"

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     $chessboard[0][$_] = "W" . $back[$_};  # White Back Row