''Purpose: meditate on how other systems/languages shaped Tcl -- started by [Richard Suchenwirth] - please add what you think!''  Of related interest is the [Tcl chronology].
----
'''UNIX shells''':
   * the names ''tclsh'', ''wish'' (specifically the ..sh ;-)

'''Bourne family of shells (sh/ksh)''':
   * cd, pwd, exec
   * separation of commands by semicolon or newline
   * separation of parameters by whitespace
   * expansion of parameters before calling the command
   * expansion of embedded commands (`..` in shells, [[..]] in Tcl which nests better) before calling the first command
   * expansion of variables with $ ($x as shortcut for [[set x]]; not in earliest Tcl, but introduced by [Karl Lehenbauer])
   * grouping of words with "", which allows expansion
   * grouping of words without expansion (Unix shells use '..', Tcl has {..} which nests better) 
   * the environment as a string->string mapping (::env array in Tcl)
   * # as comment marker
   * redirection of stdout and stdin

'''BSD's csh family of shells''':
   * tilde expansion (~suchenwi or ~/bin..)
   * redirection of stderr
   * history command

'''UNIX tools''':
   * expr (though Tcl's is much more powerful)
   * dash as switch marker (ls -l, glob -nocomplain)
'''Assembler:'''
   * ''incr'' (GfA Basic had that too, but assemblers were way earlier ;-)

'''Awk/Lex/Egrep:'''
   * regular expressions, ''[[regexp]]'', ''[[regsub]]''. (But ''[[switch -regexp]]'' really feels like something from Snobol or Trac!)

'''Awk:'''
   * associative arrays (Yes, I know, Snobol had them first, too!)

'''C''':
   * ''stdin, stdout, stderr''
   * ''argv'' (argc unneccessary, we have ''[[llength $argv]]'')
   * ''for'' loop, ''while''
   * fopen, fputs, fgets, fclose, ftell - minus the leading f
   * sprintf is ''format'', especially the format string syntax
   * putting code blocks in braces (but much more generalized in Tcl)
   * ''expr'' syntax (infix operators, functions, parens..)

'''C++''':
   * the name::space syntax (not exactly the most beautiful, tho)
'''FORTRAN''':
   * parens as marker for array elements (but different functionality)
   * ''if'' statement (well, they had that earlier than C ;-)

'''LISP''':
   * lists as major data structure (though not implemented as chains of cons cells)
   * dynamic handling of list lengths
   * Polish notation, command is always first word
   * dynamic binding of commands, rename, replacing proc's at run time, code as data, ''[[eval]]''.

'''[[Incr Tcl]]'''
   * Namespaces

'''X Window System:'''
   * the event model (as opposed to either multithreading or PL\I-style ''on''-units).
   * resource "database"
'''(not sure)''' (but all quite important to the character of the language; we need to ask John or Brent or Karl)
   * uplevel, upvar
   * info
   * trace
----
Updates by:
''KBK'' (7 November 2000) - 
''LV'' (Nov. 07/08, 2000) - [CL] (2001 ...)
----
See also [Is Tcl different!] - [Arts and crafts of Tcl-Tk programming]