"ReviewsCorpusReader" extracts feature annotations of the form label followed by a bracketed signed digit (e.g. a label then "[+2]") from each review line, using the module-level "FEATURES" regex. The feature-label sub-pattern is unbounded — an optional greedy run of word-plus-whitespace groups followed by another word, which must then be followed by a literal "[". On a long bracket-less line the label can match from every search position to the end of the line, causing quadratic backtracking. A single crafted line in a reviews corpus hangs "reviews()", "features()", and "sents()".