You cannot create variables on the fly while using strict. The solution is to use a hash instead.

my %config_hash;
my @config_vars = qw/db prefix template use_db list_mail sub_method em
+ail_method debug_level subscription_thanks_copy campaign_type/;
for (@config_vars) {
  $config_hash{$_} = $supporters_conf::config->{$_};
}
[download]