libmono-system4.0-cil 2.10.8.1-1ubuntu2.3 (amd64 binary) in ubuntu precise

 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 BCL (Base Class Libraries) of Mono for CLI 4.0.