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.
