key_released
This function checks if a particular key on the keyboard has just been released.
bool key_released(int key)
Parameters:
key
One of the BGT key name constants, see appendix A for a full list.
Return value:
true if the key has just been released, false if it has not or if an error occurs.
Remarks:
The difference between key_up and key_released is that key_released will only return true when the user first releases the key, while key_up will continue returning true until the key is down.
Example:

    // Speak a message when the space bar is released.

    void main()
    {
    tts_voice voice;
    show_game_window("Test Game");
    while(true)
    {
    if(key_pressed(KEY_SPACE))
    {
    voice.speak_interrupt("Space bar pressed.");
    }
    if(key_released(KEY_SPACE))
    {
    voice.speak_interrupt("Space bar released.");
    }
    if(key_pressed(KEY_ESCAPE))
    {
    exit();
    }
    // Other code goes here.
    wait(5);
    }
    }