When you say the original doesn't work, what makes you think it isn't?

It seems your simplified fragment is not demonstrating the problem, because:

#!/usr/bin/perl -w
                                                                      
+          
# Strict
use strict;
use warnings;
                                                                      
+          
# Libraries
use Carp;
use Data::Dumper;
                                                                      
+          
                                                                      
+          
my %drink;
# other attribute hashes
                                                                      
+          
set('larry', 'drink', 'Old Speckled Hen');
print $drink{'larry'}, "\n";
# print "Dump(\%drink) => [%s]\n", Dumper(\%drink);
                                                                      
+          
                                                                      
+          
sub set {
   my ($key, $attr, $value) = @_;
                                                                      
+          
   my $hashref;
   eval "\$hashref = \\\%$attr";
                                                                      
+          
   if ( !defined $hashref ) {
      carp 'Invalid attribute name';
   }
   else {
      $hashref->{$key} = $value;
   }
}
[download]

is working for me:

% prog541345.pl
Old Speckled Hen
[download]

If that isn't what you're getting, please compare the above code fragment (based on what you provided in your post) to your actual code, and see if that helps locate the problem.