use warnings;
use strict;
use PDL;
use PDL::NiceSlice;

#fancy matrix
#set to a blank 3d test matrix

my $matrix = zeroes 7,7,3;

#set some values for matrix

$matrix( pdl( 0..2, 4..6 ), 4, 0:2 ) .= 1;
$matrix( 4, pdl( 0..2, 4..6 ), 0:2 ) .= 1;

#the conditional problem child

my $ind = $matrix-> whichND( $matrix == 1 );

if ( all $matrix-> indexND( $ind ) == 1 ) {
    print "it worked\n";
}