Perl error global symbol requires explicit package name

Question

I have written a code to access a nested data (very complicated) data structure in perl.

<%method searchFeatureInFG>
<%args>
$featureGroup
$featureNameHash
</%args>
<%init>
my $foundFeature = 0;
my $foundGroup = undef;
my $foundIndex = undef;
if(defined $featureGroup && defined $featureNameHash){
  for(my $i = 0; $i < @$featureGroup; $i++){
    #print "<pre>".Data::Dumper::Dumper($featureGroup->[$i]->{'features'})."</pre>";
    if(ref($featureGroup->[$i]) eq 'HASH'){
        if(defined $featureNameHash->{$featureGroup->[$i]->{'name'}}){
            $foundGroup = $featureGroup;
            $foundIndex = $i;
            $foundFeature = 1;
        }
        elsif(defined $featureGroup->[$i]->{'features'}){
          for(my $j = 0; $j<scalar @{$featureGroup->[$i]->{'features'}} ; $j++){
            for(my $k=0;$k<scalar @{$featureGroup->[$i]->{'features'}->[$j]->{'features'}};$k++) {
                if (defined $featureGroup->[$i]->{'features'}->[$j]->{'features'}->[$k]->{'name'}) {
                     print $featureGroup->[$i]->{'features'}->[$j]->{'features'}->[$k]->{'name'}."\n";
                    }
            }
            last if !defined $featureGroup->[$i+1]->{'features'};
            }
    }
    }
    }elsif(defined $featureNameHash->{$featureGroup->[$i]}){
            $foundFeature = 1;
            $foundGroup = $featureGroup;
            $foundIndex = $i;
    }
    last if($foundFeature);
  }
}
return ($foundFeature, $foundGroup, $foundIndex);

</%init>
</%method>

This gives me errors like the following.

Global symbol "$i" requires explicit package name at
Global symbol "$foundFeature" requires explicit package name at 
Global symbol "$foundGroup" requires explicit package name at 
Global symbol "$featureGroup" requires explicit package name at
Global symbol "$foundIndex" requires explicit package name at 

What does these errors mean ?

Answer 1

You are getting these errors because of scoping issues. Take a look at the first one

Global symbol "$i" requires explicit package name at

You initially define $i in the line

  for(my $i = 0; $i < @$featureGroup; $i++){

But then later try to use it outside of that for loop. Perl is giving you these errors (probably because you are using strict like you should) because $i is only defined inside that for loop.

To fix this move those variable definitions outside of any scoped loops, i.e. immediately after <%init> declare

my $i
my $foundFeature
...