function SubStr(buf, start) {
// third argument (optional)
var length = 0;
var sz = 0;

sz = len(buf);

if (arrayLen(arguments) EQ 2) {

if (start GT 0) {
length = sz;
} else if (start LT 0) {
length = sz + start;
start = 1;
}

} else {

length = Arguments[3];
if (start GT 0) {
if (length LT 0)   length = 1+sz+length-start;
} else if (start LT 0) {
if (length LT 0) length = length-start;
start = 1+sz+start;

}
}

if (isNumeric(start) AND isNumeric(length)
 AND start GT 0 AND length GT 0)
return mid(buf, start, length);
else return "";
}

substr(buffer, 2) = #substr(buffer, 2)#
substr(buffer, -2) = #substr(buffer, -2)#
substr(buffer, 1, 3) = #substr(buffer, 1, 3)#
substr(buffer, 2, 4) = #substr(buffer, 2, 4)#
substr(buffer, 2, -3) = #substr(buffer, 2, -3)#
substr(buffer, -4, 2) = #substr(buffer, -4, 2)#
substr(buffer, -4, -1) = #substr(buffer, -4, -1)#