libreadonly-perl 1.03-0ubuntu1 (i386 binary) in ubuntu gutsy

 This is a facility for creating non-modifiable variables. This is
 useful for configuration files, headers, etc. It can also be useful
 as a development and debugging tool, for catching updates to variables
 that should not be changed.
 .
 If any of the values you pass to Scalar, Array, or Hash are
 references, then those functions recurse over the data structures,
 marking everything as Readonly. Usually, this is what you want: the
 entire structure nonmodifiable. If you want only the top level to be
 Readonly, use the alternate Scalar1, Array1 and Hash1
 functions.
 .
 Please note that most users of Readonly will also want to install a
 companion module Readonly::XS.