Testing Hash with empty value in HoH

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi,
With this code

#!/usr/bin/perl -w
use strict;
use Data::Dumper;


my $hoh  = { 
              'pk1' => {
                          'sk1' => [
                                     'val1',
                                     'val2'
                                   ],
                          'sk2' => {
                                      'tk1' => 'val1 val2 ',
                                      'tk2' => 'val9,val7'
                                   },
                           'sk3' => 'val10 val11',
                            'sk4' => 21
                        },
 
          'pk2' => {},
        }; 
#print Dumper $hoh;


foreach my $k ( keys %{$hoh} ) 
{

    if( $hoh->{$k} ) 
    {
       print "$k\n";
    };
    
}
[download]

How can I make it only print "pk1" since "pk2" has no value in it, without having to go through second loop. What's wrong with my test above? Now it prints both "pk1 and pk2"

Comment on Testing Hash with empty value in HoH Download Code

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Re: Testing Hash with empty value in HoH by salva (Canon) on Jun 15, 2005 at 10:16 UTC
a reference to an empty hash is a true value. Use `values` on scalar context to get the number of elements on the hash: `foreach my $k ( keys %{$hoh} ) { if( $hoh->{$k} and values %{$hoh->{$k}}) { print "$k\n"; }; }` [download] updated following Limbic~Region advice.	[reply] [d/l] [select]
Re^2: Testing Hash with empty value in HoH by Limbic~Region (Chancellor) on Jun 15, 2005 at 12:40 UTC
salva, I agree with what you have said and how you have used your code, but for clarity believe you should add in scalar context. It may not be obvious to someone unfamiliar with Perl's DWYMery that in list context you get the list of values and in scalar context you only get the count. Cheers - L~R	[reply]
Re: Testing Hash with empty value in HoH by dorward (Curate) on Jun 15, 2005 at 10:18 UTC
A reference to a hash, even an empty hash, is true. Try defreferencing it. `my $foo = {}; print "OK\n" if (scalar %{$foo});` [download]	[reply] [d/l]
Re: Testing Hash with empty value in HoH by monkey_boy (Priest) on Jun 15, 2005 at 10:16 UTC
In your data structure change: `'pk2' => {},` [download] to: `'pk2' => undef,` [download] or `if( $hoh->{$k} )` [download] to: `if( keys %{$hoh->{$k}} )` [download] This is not a Signature...	[reply] [d/l] [select]

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