[AMG]: In Tcl and in many command line programs, `--` is "the switch to end all switches" ([RS]). See ['--' in Tcl] for more information on this usage. In C and a few related languages, `--` is the decrement operator. In Tcl, use [[`[incr]` var -1]] to decrement a variable and return its new value. To decrement and return the prior value, combine with `[K]`, e.g.: ====== proc K {a b} {return $a} puts [K $var [incr var -1]] ====== In email, `--` followed by space then newline is the traditional separator between an email message and the signature. In many command line programs (typically not Tcl programs), `--` is the prefix for [GNU]-style long options, those being options (switches) spelled out with names longer than a single character. For example, "`[ls] --almost-all`" is a more verbose way to say "`ls -A`". <> Syntax