prerm is in watchdog 5.15-2.
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  | #!/bin/sh
set -e 
if [ \( "$1" = "upgrade" -o "$1" = "remove" \) -a -L /usr/doc/watchdog ]; then
        rm -f /usr/doc/watchdog
fi
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