my $mem_dbh = DBI->connect('dbi:SQLite:dbname=:memory:');
$mem_dbh->sqlite_backup_from_file($db_file_name);

# process, process, process...

# Don't forget to copy the in-memory data back to disk if
# you've made any changes that should be persistent; if not,
# skip this step.
$mem_dbh->sqlite_backup_to_file($db_file_name);