Return from a subroutine generates a negative value

[c]

I have the following subroutine:

sub get_latest_avg {
  my $host = shift;
  my $rrd = shift;
  my $type = shift;
                                                                      
+          
  my $snmp = Net::SNMP->session(
                -hostname       => $host,
                -version        => '1',
                -community      => $nodes{$host}->{community}, );
                                                                      
+          
  my $num = $snmp->get_request( -varbindlist =>   [$rrd{$rrd}{$type}] 
+)                                                                    
+            ;
                                                                      
+          
  my $avg = $num->{$rrd{$rrd}{$type}};
                                                                      
+          
  $snmp->close;
                                                                      
+          
  return $avg;
                                                                      
+          
}

I call this subroutine from within another for loop:

for my $host(keys %nodes) {
  for my $rrd(keys %rrd) {
    my $avg = &get_latest_avg($host,$rrd,'free');
    print $avg. "\n";
  }
}

I've confirmed each of the variables are assigned correctly through various print statements in key places. What is unusual is that no matter how i order the keys of %rrd, only the first pass returns a valid value. The remaining passes over the other keys return '-1' as the value.

Your input is very appreciated. -c