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    my @L = map {
        fix($_->[4]);
...
    } map {
        [ split ]
    } <F>; 

$ cat foo.txt | fgrep blah

$ fgrep blah <foo.txt | consolidate | dump
$ preproc <foo.txt | fgrep blah | consolidate | dump
...
$ cat foo.txt | preproc | fgrep blah | consolidate | dump
$ cat foo.txt bar.txt | additional | preproc | fgrep blah | consolidat
+e | dump
$ real_stream | additional | preproc | fgrep blah | consolidate | dump