$ perl -Mstrict -Mwarnings -E '
    my @dd = (
        [ qw{ r0c0 r0c1 r0c2 } ],
        [ qw{ r1c0 r1c1 r1c2 } ],
    );
    my $number_of_rows = @dd;
    say "No. of rows: $number_of_rows";
    my $number_of_columns = @{ $dd[0] };
    say "No. of columns: $number_of_columns";
'
No. of rows: 2
No. of columns: 3