''from a posting on news:comp.lang.tcl by [Paul Duffin] (much more of his thoughts is on http://www.cs.man.ac.uk/~fellowsd/tcl/future.html ):''

'''Syntactically / Semantically'''
   * Everything can be a string (used to be "Everything is a string") 
   * Everything is done using commands.
   * The $ sign is only a convenient shortcut for the "[[set ...]]" command. - '''FP'''
   * All commands are treated equally.
   * A command is a sequence of whitespace separated words.
   * Each word in a command is treated the same (*before* passing to the command).
  
'''Conceptually'''
   * No artifical limits.
   * Provide simple building blocks.
   * Things should be as general as possible.
  
'''Community'''
   * Use the best tool for the job. Often Tcl can be the best tool but not always.
  
'''I/O'''
   * Event driven is good.

'''GUI'''
   * Event driven is good.
  
'''Threading'''
   * Threads are really little processes inside a big process and therefore should be isolated/protected from one another.
   * Data shared between threads should be explicitly requested.
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'''Internationalization'''
   * Unicode is good, for just about every language.
   * UTF-8 is good for representing Unicode, when most often you have low-ASCII characters. (RS)
'''Error handling'''
   * Error messages should be helpful and friendly.
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See also [The Tao of Tcl]