Perl module that keeps insertion order in hash

 Tie::DxHash implements a hash which preserves insertion order and allows
 duplicate keys.
 .
 Tie::DxHash works by storing the hash data in an array of hash references
 (containing the key/value pairs). This preserves insertion order. A
 separate set of iterators (one per distinct key) keeps track of the last
 retrieved value for a given key, thus allowing the successive retrieval of
 multiple values for the same key to work as expected.
 .
 Tie::DxHash was originally written to facilitate the use of more complex
 mod_rewrite rules in Apache configuration files written with Perl Sections.