prerm is in joe 3.7-2.3ubuntu1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 | #!/bin/sh -e
if [ "$1" != "upgrade" ]; then
  update-alternatives --remove editor /usr/bin/joe
  update-alternatives --remove editor /usr/bin/jmacs
  update-alternatives --remove editor /usr/bin/jstar
  update-alternatives --remove editor /usr/bin/jpico
  update-alternatives --remove editor /usr/bin/rjoe
fi
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