Detect iOS version less than 5 with JavaScript

This is related to the "fix" for position:fixed in older versions of iOS. However, if iOS5 or greater is installed, the fix breaks the page.

I know how to detect iOS 5: navigator.userAgent.match(/OS 5_\d like Mac OS X/i) but that won't work for iOS6 when it eventually comes around, or even iOS 5.0.1, only a 2 digit version.

So this is what I have atm.

$(document).bind("scroll", function() {
    if((navigator.userAgent.match(/iPhone/i)) || (navigator.userAgent.match(/iPod/i)) || (navigator.userAgent.match(/iPad/i))) {
        if (navigator.userAgent.match(/OS 5_\d like Mac OS X/i)) {
    }
    else {
        changeFooterPosition();
    }
});