[jQuery] return var from $.get

Hi

Im newbie with Javascript/jQuery so this question may be lame...

I have something like that:

$.get('istracked.php',{'code': code}, function(data) {
if (data=='true')
{
    r=true;
}
});

How can I use "r" outside $.get ?
$.get returns XMLHttpRequest

at the moment I know only one solution:
inside of $.get:
$('body').append('<span class="temp" style="display: none;">'+r+'</
span>');

and outside
r=$('span.temp').html();

Do you know how to solve my problem in proper way?

TIA
Michael