The variable tcl_platform(debug) has been added. If the
variable exists, it indicates that the Tcl shell has been
compiled with debug information. (Windows platform only)

The fconfigure command has a new -error option that returns the
current error status of a socket. This is useful when you need
to determine if an asynchronous connect operation succeeded. If
there was an error, the error message is returned. If there was
no error, an empty string is returned.

The bind command has a new MouseWheel event that will fire
in response to mouse wheel movement. You can bind to the
MouseWheel event and use the %D substitution to get the delta
the wheel moved. (Windows platform only)

The event generate command has been enhanced with the -delta
flag so you can generate MouseWheel events from Tcl. The listbox
and text widgets' default bindings have been updated to
understand MouseWheel events. (Windows platform only)

Tcl group at Sun was disbanded. The site may disappear in the
future, but currently it redirects users to http://www.scriptics.com.

Additions for Tcl/Tk 8.1

Tcl/Tk 8.1 final, released in April 1999, is a significant new release.
The major new features include:

support for multi-threaded applications
support for internationalization based on Unicode
a new, more powerful, regular expression package
improved extension architecture
new message catalog package
DDE support on Windows platform
library of C procedures for widget configuration options
additional object-based C library procedures
Tk embedding now also works on the Macintosh
better support for binary data based on UTF-8

New Tcl Core Commands

The following new commands have been added:

dde: execute a Dynamic Data Exchange command
encoding: convert between different character encoding systems
msgcat: message catalog to support internationalization

Modified Commands

The following commands have been modified:

fconfigure: now supports a -encoding option for specifying the
encoding of an open file or socket.
pkg_mkIndex: has new -direct option to generate direct loading
package indexes.
string: has a totitle subcommand to convert strings to have first
character capitalized and remainder lowercase.
regexp: now accepts three new switches -line, -lineanchor, and
-linestop that control how regular expressions treat
line breaks.
scan: now supports XPG3 position specifiers and the "%n" conversion
character.

The global variable tcl_platform(user) returns the name of the current user.

New Tcl/Tk API Functions

Many additions and changes have been made. They are described in the
following documentation pages: Access, ByteArrObj, Encoding, EvalObj,
GetCwd, GetVersion, InitStubs, ObjSetVar, ParseCmd, SaveResult, Thread,
ToUpper, Utf, InitStubs, SetOptions.