Turns ON or OFF the expanding of aliases in the inputline, If you set INPUT_ALIASES ON and type: ECHO $S you will see your server name echoed to your window. If it is OFF, you will see $S echoed to your window. INPUT_ALIASES now has no effect on expansions in the .ircrc and loaded files. To Make a line expand when a file is loaded, use EVAL <command>.
Note also, that when INPUT_ALIASES is ON, text within (..) and {..} are not expanded. If you want them to be expanded then quote the leading ( or {. e.g. \( \{
Additionally, You can return to full alias substitution within ${...} by enclosing the substitution text in [...]. Thus if $0 == test, and $bear == black
${[$0]} expands to "test"
${[$bear]} expands to "black"
${bear} also expands to "black"
${ bear == [black] } expands to "1",
${ [$0] == [test] } expands to "1"
${ [$0] == [black] } expands to "0"
${ [$0](this) } expands to the return value of $test(this)
Note:
If you do turn on INPUT_ALIASES in the .ircrc then the argument
expandos ($*, $0, $1, $3-4, etc) will expand to the command line
arguments passed to IRCII on startup.