Bug fix: Introduce new scope in case clauses
Add VM.Subr
Add Insn.Check
Improve error message of match failure
Bug fix: Compiler.compile_body
Add module: Pattern
Add Insn.BeginModule & Insn.EndModule
Add Insn.ExportVar & Insn.ExportMethod
Add Insn.Open
Add Insn.Include
Add Insn.ReturnModule
Add Insn.UnexportVar & Insn.UnexportMethod
Rewrite Builtin
Change signature of subr