POSTIN

/bin/sh

update-alternatives --install /bin/vi vi /usr/bin/vim-enhanced 20 \
    --slave /bin/view view /usr/bin/vim-enhanced \
    --slave /bin/ex ex /usr/bin/vim-enhanced \
    --slave /bin/rvi rvi /usr/bin/vim-enhanced \
    --slave /bin/rview rview /usr/bin/vim-enhanced
update-alternatives --install /bin/vim vim /usr/bin/vim-enhanced 20 \
    --slave /bin/rvim rvim /usr/bin/vim-enhanced

POSTUN

/bin/sh

[ $1 = 0 ] || exit 0
update-alternatives --remove vi  /usr/bin/vim-enhanced
update-alternatives --remove vim /usr/bin/vim-enhanced

Triggers

vim-enhanced < 7.3

/bin/sh

update-alternatives --remove uvi /usr/bin/vim-enhanced