use strict;
use warinings;
use PDL;
use PDL::NiceSlice;

sub submatrix_sum {
    my $m = pdl @_;

    $m->range(ndcoords($m(1:,1:)), 2)->reorder(2, 3, 0, 1)
        ->clump(2)->sumover;
}

##</code><code>##

sub submatrix_sum {
    my $w = shift;
    my $h = shift;
    my $m = pdl @_;

    $m->range(ndcoords($m($w - 1:, $h - 1:), [$w, $h])->reorder(2, 3, 0, 1)
        ->clump(2)->sumover;
}