**Object Oriented Programming** The commands of the '''[TclOO]''' package are now part of Tcl itself. This gives Tcl a built-in object system that is fully dynamic, class-based, and includes advanced features such as meta-classes, filters, and mixins. New version 4 of the popular package Itcl (aka '''incr Tcl''') is also included, granting support for some traditional OO Tcl programming out of the box as well. **Stackless Evaluation** The evaluation of many levels of nested '''proc''' calls are no longer implemented as a stack of nested C routine calls. This revision in the internal implementation of Tcl evaluation makes deep recursion in Tcl scripts safe to do. But there's more... This new implementation enables a collection of new commands, '''coroutine''', '''tailcall''', '''yield''', and '''yieldto''' that provide profound new capabilities and models of concurrency to Tcl scripts. **Enhanced Exceptions** New commands '''try''' and '''throw''' and a wealth of new '''-errorcode''' values enable far more precise trapping and handling of exceptions using a familiar construct. **Batteries Included** Tcl delivers in the '''pkgs''' subdirectory a bundled collection of third-party packages built and installed along with Tcl. **Thread-enabled Operations** A thread-enabled default build, a bundled '''Thread''' package, and new command '''interp cancel''' make Tcl 8.6 ready for your multi-threaded programming tasks. **SQL Database Powered** The bundled Tcl DataBase Connectivity ('''tdbc''') interface package makes it possible to write your SQL database-powered scripts decoupled from any particular database engine. The bundled '''sqlite3''' and '''tdbc::sqlite3''' packages supply a powerful and popular SQL database engine ready to use. **IPv6 Networking** The '''socket''' command now recognizes numeric IPv6 addresses as valid values for its ''$host'' argument where platform support exists. **Built-in Zlib Compression** New command '''zlib''' provides utilities to handle compression of data and streams. **List Processing** New commands '''lmap''' and '''dict map''' enable the elegant expression of transformations over Tcl containers. **Stacked Channels by Script** New commands '''chan push''' and '''chan pop''' expose the power of stacked channels without the need to write C code. **Other New Features** Temporary '''file''' creation, enhancements to list sorting and setting, '''dict''' filtering, half-close of bidirectional channels, encoding and decoding of '''binary''' sequences, finer control over '''load''', and many many more. Every new feature is important to somebody. See [Changes in Tcl/Tk 8.6] or [http://tip.tcl.tk/311%|%TIP #311] for the complete list. <>Documentation | Changes in Tcl/Tk