#!/usr/bin/perl

# http://perlmonks.org/?node_id=1211497

use strict;
use warnings;
use Data::Dump 'pp';

sub up
  {
  my ($row, $col) = $_[0]->@*;
  return $row == 0 && $col == 0 ? [ map [ @$_ ], @_ ] :
    (($row > 0 && $col > 0 ? up( [ ~-$row, ~-$col ], @_ ) : () ),
      ($row > $col ? up( [ ~-$row, $col ], @_ ) : () ) );
  }

pp up [ 3, 1 ];

##</code><code>##

(
  [[0, 0], [1, 0], [2, 0], [3, 1]],
  [[0, 0], [1, 0], [2, 1], [3, 1]],
  [[0, 0], [1, 1], [2, 1], [3, 1]],
)