I'd like to have an identifier for $input.

var %i = $input("Which names",e,names,%names)
if ( %i != $null ) { set %names %i }

mirc doesn't know if you pressed the ok button or the cancel button when you typed nothing in the editbox.

When you try to delete all the names in %names, it would reject because %i = $null. If you don't use the if-statement you also save the settings when someone is pressing cancel.