XVII. DBM Functions
    These functions allow you to store records stored in a dbm-style
    database. This type of database (supported by the Berkeley DB,
    GDBM, and some system libraries, as well as a built-in flatfile
    library) stores key/value pairs (as opposed to the full-blown
    records supported by relational databases).
   
    
Example 1. DBM example 
$dbm = dbmopen ("lastseen", "w");
if (dbmexists ($dbm, $userid)) {
    $last_seen = dbmfetch ($dbm, $userid);
} else {
    dbminsert ($dbm, $userid, time());
}
do_stuff();
dbmreplace ($dbm, $userid, time());
dbmclose ($dbm);
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   - Table of Contents
 - dbmopen — Opens a DBM database
 - dbmclose — Closes a dbm database
 - dbmexists — 
     Tells if a value exists for a key in a DBM database
    
 - dbmfetch — 
     Fetches a value for a key from a DBM database
    
 - dbminsert — 
     Inserts a value for a key in a DBM database
    
 - dbmreplace — 
     Replaces the value for a key in a DBM database
    
 - dbmdelete — 
     Deletes the value for a key from a DBM database
    
 - dbmfirstkey — 
     Retrieves the first key from a DBM database
    
 - dbmnextkey — 
     Retrieves the next key from a DBM database
 - dblist — 
     Describes the DBM-compatible library being used