Maybe something like this

function go
{
    if [ $1 = "--add" ];then
             
        perl -pi -ne 's/^\(UNKNOWN/($2) cd $3;;\n(UNKNOWN/' ~/.bashrc
            
    fi

    case $1 in
        (tmp)  cd $HOME/tmp;;
        (home) cd $HOME/home;;
(UNKNOWN) true ;;
    esac

}
[download]

Though actually I don't like the idea