In Tcl, these strings are taken as logical false:

  • 0 (the canonical form, like in C)
  • no
  • off
  • false

Also allowed are case-insensitive equivalents (i.e., "FaLSe") as well as the unambiguous abbreviations n for no, of for off (but not just o!), and f, fa, fal and fals for false. Other numeric forms equivalent to 0 (i.e., 0.0, 0x0, 0e0, or 0e# or 0e-#).

See also true, string is false.