Dear Monks,

this is probably simple, but still I am stuck. How do you access a hash through its hash reference and test if part of it (a subhash) exists? What I would like to do is print individuals only if coordinate information is available for them. Information about the individuals is stored in one hash accessed through a hash reference, coordinate information in another hash accessed through a hash reference. This is the code: 

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
                
            }
        }
    }

}

[download]

Running it results in: "Can't use string ("") as a HASH ref while "strict refs" in use at ...

I have been struggling with this for a while and would be very happy if you could help me with it. Henri

In reply to Test if a subhash in a referenced hash exists by Henri

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