I have a fairly perplexing problem with accessing a value in a 2d hashref. Even though Data::Dumper shows that $self->{established}->{intro_rec} does exist within the hashref, attempt to access this value fail, as indicated by the two warnings (Use of uninitialized value in sprintf at blib/lib/AI/Proplog.pm line 70.) as well as by the fact that the output of the sprintf is empty. However, this is perplexing because the Data::Dumper output on the same line shows these values as existing.

There is one peculiar thing about the particular element I want to access. It was added during the second time I added things to this element of the hashref. However, a similar sample program (where I add a set of elements, then later add another set of elements) worked fine.

Source code

sub satisfied {
    my ($self, @body) = @_;

    if ($debug) {
        warn sprintf "TESTING @body in satisfied() with self-e: %s",
      Data::Dumper::Dumper($self->{established});
    }

    for my $prop (@body) {
        if ($debug) {
            warn sprintf "prop($prop): %s dr: %s dr2: %s dump: %s",
            $prop,
            $self->{established}->{$prop},
            $self->{established}->{intro_rec},
          Data::Dumper::Dumper($self->{established});
        }
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Debug output

TESTING intro_rec comp_org adv_prog theory in satisfied() with self-e:
+ $VAR1 = \
{
          'adv_prog' => '1',
          'intro_cs' => '1',
          'theory' => '1',
          'comp_org' => '1',
          'intro_req' => '1'
        };
Use of uninitialized value in sprintf at blib/lib/AI/Proplog.pm line 7
+0.
Use of uninitialized value in sprintf at blib/lib/AI/Proplog.pm line 7
+0.
prop(intro_rec): intro_rec dr:  dr2:  dump: $VAR1 = {
          'adv_prog' => '1',
          'intro_cs' => '1',
          'theory' => '1',
          'comp_org' => '1',
          'intro_req' => '1'
        };
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Attempt to reproduce the problem in simpler circumstances (works fine unfortunately)

package X;

use strict;

sub printlist {
    my ($self, @L) = @_;

    for my $prop (@L) {

        if ($self->{established}->{$prop}) {
            warn "$prop established";
        } else {
            warn "$prop NOT established";
        }
    }
}
my $self = {} ;

bless $self, 'X';

my @L = qw(intro_cs comp_org adv_prog theory);
my @M = qw(intro_req);

$self->{established}->{$_}++ for @L;

$self->printlist(@L);

$self->{established}->{$_}++ for @M;

$self->printlist(@M);
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