To get a list of methods and variables from child.pm, I would use Devel::Symdump. Here's an example:

#!/usr/bin/perl 

use strict;
use warnings;
use Data::Dumper::Concise;

require Devel::Symdump;

my @packs = qw(Data::Dumper::Concise);
my $obj   = Devel::Symdump->new(@packs);

my @array = $obj->scalars;
@array = $obj->arrays;
@array = $obj->hashes;

my $string = $obj->as_string;
print $string, "\n";
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I substituted Data::Dumper::Concisefor Grandparent::Parent::Child; also, make sure that you "use" the package just below use warnings.