/usr/share/postgresql/9.1/extension/prefix.control is in postgresql-9.1-prefix 1.1.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | # prefix extension
comment = 'Prefix Range module for PostgreSQL'
default_version = '1.1'
module_pathname = '$libdir/prefix'
relocatable = true
|