sub _fork {        
    ### safely sync/close databases, close environment ###
    _untie_shared_vars();
    _close_BerkeleyDB_env();

    ### do the fork ###
    my $pid = CORE::fork;
        
    if (!defined $pid || $pid) { #in parent
        ### re-open environment and immediately retie shared variables ###
        _open_BerkeleyDB_env();
        _tie_share_vars();
    }
    elsif ( $pid == 0 ) { # in child
        ### open environment and immediately tie shared variables ###
        _open_BerkeleyDB_env();
        _tie_share_vars();
    }
    else {
        croak( "Unable to fork" );
    }

    return $pid;
};