function first(delimiter)
{
	var elements=this.split(delimiter,1);
	return(elements[0]);
}
function rest(delimiter)
{
	var p=this.indexOf(delimiter);
	return(p==-1?"":this.substr(p+delimiter.length));
}
function last(delimiter)
{
	var p=this.lastIndexOf(delimiter);
	return(p==-1?this:this.substr(p+delimiter.length));
}
function word(delimiter,number)
{
	var elements=this.split(delimiter);
	return(elements.length<number?"":elements[number-1]);
}
function leftback(delimiter)
{
	var p=this.lastIndexOf(delimiter);
	return(p==-1?"":this.substr(0,p));
}
String.prototype.first=first;
String.prototype.rest=rest;
String.prototype.last=last;
String.prototype.word=word;
String.prototype.leftback=leftback;