That would depend on how you arrange the rows and columns in your array; however, if you use (what I'd consider) the normal way, then @double_dimension_array in scalar context will return the number of rows. Furthermore, assuming a gridded or table structure, where each row has the same number of columns, @{ $double_dimension_array[0] } in scalar context will return the number of columns.

$ 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
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