The $! identifier returns the input value that the script was just given via user input. This operation can also save you on writing in a variable, which isn't always an option but it is good to know when it can be useful.

Example

alias testme {
  $?="Type something"
  echo -a $!
}

After you execute the alias, via /testme, you will be prompted by an input box. Whatever input you put in that box, upon clicking OK, will be immediately echoed to your active window.