So congratulations and many many thanks !
Merci

I reworked your code some and the following was a little better than twice as fast for my test cases:

String.prototype.xSplit = function(_regEx){
// Most browsers can do this properly, so let them — they'll do it faster
if ('a~b'.split(/(~)/).length === 3) { return this.split(_regEx); }

if (!_regEx.global)
{ _regEx = new RegExp(_regEx.source, 'g' + (_regEx.ignoreCase ? 'i' : ")); }

// IE (and any other browser that can't capture the delimiter)
// will, unfortunately, have to be slowed down
var start = 0, arr=[];
var result;
while((result = _regEx.exec(this)) != null){
arr.push(this.slice(start, result.index));
if(result.length > 1) arr.push(result[1]);
start = _regEx.lastIndex;
}
if(start < this.length) arr.push(this.slice(start));
if(start == this.length) arr.push(""); //delim at the end
return arr;
};