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.