Manual:

Reference:

-- Perl 5.8.8 documentation --

DBM_Filter::int32

    use SDBM_File; # or DB_File, or GDBM_File, or NDBM_File, or ODBM_File
    use DBM_Filter ;

    $db = tie %hash, ...
    $db->Filter_Push('int32');

This DBM filter is used when interoperating with a C/C++ application that uses a C int as either the key and/or value in the DBM file.