#!/usr/bin/perl -w
use strict;

use mapcar;

sub neighbors {
    my @coords= @_;
    my @offset= (-1) x @coords;
    return sub {
        my $i= 0;
        return   if  ! @coords;
        my @return= mapcar { $_[0] + $_[1] } \@coords, \@offset;
        while(  1 < ++$offset[$i]  ) {
            $offset[$i]= -1;
            if(  $#offset < ++$i  ) {
                @offset= @coords= ();
                last;
            }
        }
        return @return;
    };
}

my $next= neighbors( 6, 2, -4 );
my @coords;
while(  @coords= $next->()  ) {
    print "( @coords )\n";
}

##</code><code>##

( 5 1 -5 )
( 6 1 -5 )
( 7 1 -5 )
( 5 2 -5 )
( 6 2 -5 )
( 7 2 -5 )
( 5 3 -5 )
( 6 3 -5 )
( 7 3 -5 )
( 5 1 -4 )
( 6 1 -4 )
( 7 1 -4 )
( 5 2 -4 )
( 6 2 -4 )
( 7 2 -4 )
( 5 3 -4 )
( 6 3 -4 )
( 7 3 -4 )
( 5 1 -3 )
( 6 1 -3 )
( 7 1 -3 )
( 5 2 -3 )
( 6 2 -3 )
( 7 2 -3 )
( 5 3 -3 )
( 6 3 -3 )
( 7 3 -3 )