use strict;
use warnings;

my $individuals = {};
my $coordinates = {};
# Fill the hashes associated with $individuals and $coordinates
# in subroutines so that
# $$coordinates{$group}{$id}{$stage}{"coords"}{$coord_no} = $value

print_coords($individuals, $coordinates);

sub print_coords {
	my ($individuals, $coordinates) = @_;

    foreach my $group (sort keys %$individuals) {
		foreach my $id (sort keys %{$$individuals{$group}}) {
	      INDIVIDUAL:
	    	foreach my $stage (sort keys %{$$individuals{$group}{$id}}) {
	    	
                # here the test
	    		if (!(%{$$coordinates{$group}{$id}{$stage}{"coords"})) {
					next INDIVIDUAL;
				}
		
				# print individual and coordinate information
				
			}
		}
	}

}