use constant {
    SELF            => 0,
    CODE_TO_RUN     => 1,
    FIRST_DAUGHTER  => 0,
    LAST_DAUGHTER   => 1,
    NEXT_SISTER     => 2,
    PREVIOUS_SISTER => 3,
    PARENT          => 4,
};


## then in your methods

sub traverse {
    if( $_[SELF][FIRST_DAUGHTER] ) {
         traverse( $_[SELF][FIRST_DAUGHTER], $_[CODE_TO_RUN] );
    }
    elsif( $_[SELF][NEXT_SISTER] ) {
         traverse( $_[SELF][NEXT_SISTER], $_[CODE_TO_RUN] );
    elsif( ... )
        ...;
    }
    return;
}

##</code><code>##


sub traverse {
    return unless defined $_[SELF];
    $_[CODE_TO_RUN]->( ... );
    $_[SELF] = $_[SELF][FIRST_DAUGHTER] 
            || $_[SELF][NEXT_SISTER]
            || undef;
    goto &traverse;     
}