yao@ubuntu:~/perl$ perl abstract_extractor_by_ting 2.txt
sort: open failed: words_in_SENTENCES: No such file or directory
uniq: SENTENCES_words_sort: No such file or directory
sh: 1: spell: not found
uniq: words_in_SENTENCES_words_comb: No such file or directory
sh: 1: spell: not found
sort: open failed: SENTENCES_WORDS_root: No such file or directory