MLDBM is a Perl module to store multi-level hash structure in single level tied hash.
use MLDBM; # this gets the default, SDBM
#use MLDBM qw(DB_File FreezeThaw); # use FreezeThaw for serializing
#use MLDBM qw(DB_File Storable); # use Storable for serializing
$dbm = tie %o, 'MLDBM' [..other DBM args..] or die $!;
This module can serve as a transparent interface to any TIEHASH package that is required to store arbitrary perl data, including nested references. Thus, this module can be used for storing references and other arbitrary data within DBM databases.
It works by serializing the references in the hash into a single string. In the underlying TIEHASH package (usually a DBM database), it is this string that gets stored. When the value is fetched again, the string is deserialized to reconstruct the data structure into memory.
For historical and practical reasons, it requires the Data::Dumper package, available at any CPAN site. Data::Dumper gives you really nice-looking dumps of your data structures, in case you wish to look at them on the screen, and it was the only serializing engine before version 2.00. However, as of version 2.00, you can use any of Data::Dumper, FreezeThaw or Storable to perform the underlying serialization, as hinted at by the SYNOPSIS overview above. Using Storable is usually much faster than the other methods.