Stuff by David - Upgrade of keyboard

Upgrade of keyboard_string
/*

    CALL:
        user_input_step()

    INFO:
        Sets the user_input variable, which acts like keyboard_string,
        but with a few improvements.

        This script must be called at least once per step in order for the
        variable to be updated correctly.

    ARGUMENTS:
        None

    WRITTEN BY:
        Davve
        http://www.stuffbydavid.com
        Credit not needed if used, but appreciated.

*/
if (!variable_global_exists('user_input')) {    //Create user_input if it doesn't exist.
    globalvar user_input, __lastlength, __press;
    user_input = '';
    __lastlength = string_length(keyboard_string);
    __press = current_time;
}
user_input += string_delete(keyboard_string, 1, __lastlength);  //Add the last typed character(s)
keyboard_string = '' + (string_length(keyboard_string) < 1024) * keyboard_string;   //If keyboard_string have met the 1024 limit, erase it.
__lastlength = string_length(keyboard_string);
if (keyboard_check_pressed(vk_backspace)) {         //Erase the last typed character with backspace.
    user_input = string_copy(user_input, 1, string_length(user_input) - 1);
    __press = current_time;
}
user_input = string_copy(user_input, 1, string_length(user_input) - (keyboard_check(vk_backspace) && current_time - __press > 450));
Comments
Constructive criticism is always welcome!