From the manual:
STR followed by a byte array variable, count and optional ending
character will receive a string of characters. The string length is
determined by the count or when the optional character is
encountered in the input.
[STR smallp\10\,]
See if that will get the first part correctly.

Does the data comming in have a qualifying character before the data you want? If so then the first example I gave will work. If it does not have a qualifying character then leave that part out.