Several issues -- first, your slice isn't a slice. You need @sortarr[0..10]. Second, the content of each element is an array reference -- you need to slice out each part of that. p.272 is throwing you off because it's giving a slice of a row -- you're trying for a slice of a column (in a row-major AoA).

You probably want to use map to extract the subslices. E.g.

my @aoa = (
    [1 .. 4],
    [5 .. 8],
    [9 .. 12],
);

my @column_slice = map { [ $_->[2] ] } @aoa[1,2];

my @two_d_slice  = map { [ @{$_}[1,2] ] } @aoa[1,2];
[download]

For a column slice, for each element of the slice, @aoa[1,2] (i.e. the rows), this dereferences the array reference to get the column, and returns it as a new anonymous array reference. (This keeps it an AoA; if you want a flattened list, omit the square brackets just inside the map braces.). For two-dimensions, it's similar, but you slice inside the map, too.