libmono-corlib1.0-cil 1.2.3.1-1ubuntu1 (amd64 binary) in ubuntu gutsy

 Mono is a platform for running and developing applications based on the
 ECMA/ISO Standards. Mono is an open source effort led by Novell.
 Mono provides a complete CLR (Common Language Runtime) including compiler and
 runtime, which can produce and execute CIL (Common Intermediate Language)
 bytecode (aka assemblies), and a class library.
 .
 This package contains the Core Library (mscorlib.dll) of Mono which is the
 glue between the Class Library and the JIT.