@param text the input text to parse, not null
@param pos the position to start parsing at, from 0 to the text
length. Upon return, position will be updated to the new parse
position, or unchanged, if no match found.
@return the resulting string, or null if no match found.
Match text with the prefix tree.
@param text the input text to parse, not null @param pos the position to start parsing at, from 0 to the text length. Upon return, position will be updated to the new parse position, or unchanged, if no match found. @return the resulting string, or null if no match found.