New packages
New Tcl commands
New Tcl subcommands
Extended syntax/new options
fconfigure channel ?... -encoding ...?
New Tcl global variables
Changed behavior
The Windows reigstry key/value which holds the root installation directory for Tcl/Tk changed (again!). To retrieve that directory from the Windows registry, use the Tcl command
registry get HKEY_LOCAL_MACHINE\\SOFTWARE\\Scriptics\\Tcl\\[info tclversion] Root
Advanced regular expressions. See regexp(n). The changes result in incompatibilities at the C API as well as potential incompatibilities in regular expressions.
Expanded scan functionality, including XPG3. See scan(n).
\ooo, \xhh, and \uhhhh escapes indicate Unicode character values.
format %c converts to Unicode; no longer limited to 8 bits.