Noob questions

Here is where I am at. I decided to make a sketch for one section of my code. The "LEFT" part using the "Blinking LED" sketch. I figured if I can make this work then the rest should be fairly straightforward. When I read that "delay" pauses everything, I realized that this won't work because I need to monitor my inputs for changes and decided to try the Blink Without Delay sketch and change things to my designations. Here is what I came up with:

const int LEFT = 5; // the number of the LED pin
const int LEFT = 6;
const int LEFT = 9;
const int LEFT = 10;
const int SWITCH = 4;

int ledState = LOW; // ledState used to set the LED
long previousMillis = 0; // will store last time LED was updated

long interval = 2000; // interval at which to blink (milliseconds)

void setup() {
// set the digital pin as output:
pinMode(LEFT, OUTPUT);
}

void loop()
{
unsigned long currentMillis = millis();

if(currentMillis - previousMillis > interval) {
// save the last time you blinked the LED
previousMillis = currentMillis;

// if the LED is off turn it on and vice-versa:
if (ledState == LOW)
ledState = HIGH;
else
ledState = LOW;

// set the LED with the ledState of the variable:
digitalWrite(LEFT, ledState);
}
}

When I "verify" it shows problems with using LEFT multiple times. From what I have read I understand that I want the Uno, whenever it see's LEFT, to know that this is an output and know that the output will be pins 5,6,9,10. I am assuming that because "verify" shows that this is a problem, that I can't use LEFT to define all 4 output pins. If that is so, how do I need to change this so that when I have an input on pin 4, I output to pins 5,6,9,10?