use Algorithm::Loops qw( NestedLoops );

my $num_objects    = 5;
my $num_containers = 3;

my $str = join('', 1..$num_objects);

NestedLoops(
    [
        [ 1 .. $num_objects-1 ],
        (sub { [ $_[-1]+1 .. $num_objects-1 ] }) x ($num_containers-2)
    ],
    sub {
        my $str = $str;
        substr($str, $_, 0, '|') for reverse @_;
        print("$str\n");
    },
);