prerm is in texlive-binaries 2015.20160222.37495-1.
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 10 11 12 13 14 | #!/bin/sh -e
# texlive-binaries postinst, created 2009 by Norbert Preining
# probably not copyrightable as it looks now, but anyway the code maybe 
# freely copied, distributed and/or modified
# deactivate the xdvi.bin alternative
case "$1" in 
  upgrade)
    ;;
  *)
    update-alternatives --remove xdvi.bin /usr/bin/xdvi-xaw
    update-alternatives --remove bibtex /usr/bin/bibtex.original
    ;;
esac
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