popd [ {+|-}n ]
       Remove an entry from the directory stack, and perform  a  cd  to
       the  new top directory.  With no argument, the current top entry
       is removed.  An argument of the form  `+n'  identifies  a  stack
       entry  by  counting  from the left of the list shown by the dirs
       command, starting with zero.  An argument of the form -n  counts
       from  the right.  If the PUSHD_MINUS option is set, the meanings
       of `+' and `-' in this context are swapped.
