Perl Quiz-of-the-Week #9

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You will write a simple spelling checker program, similar to the Unix
'spell' utility.

The program should be called 'spel'.  It will read a document from
standard input and print on standard output a list of all the
misspelled words in the document.  If any command line arguments are
given, 'spel' should read those files instead of the standard input.

The output words should be in lexicographic order, and no word should
appear more than once in the output.

'spel' will be given one or more dictionaries of words that are
already spelled correctly.  It will always try to read the file
'/usr/dict/words'.  It will also try to read '.spel' files from
certain directories.  If the user has set an environment variable
SPELWORDS, 'spel' should interpret its value as a :-separated list of
directories to be searched for '.spel' files.  If no SPELWORDS
variable is set, 'spel' should search in the user's home directory and
in the current directory.

If you need a sample dictionary, you can obtain one from 

        http://perl.plover.com/qotw/words/

* * * 

P.S.: I'm sorry that this week's quiz (and last week's reports) are
late.  I was detained all through Tuesday and Wednesday by other
business.  I hope to send out last week's reports tonight.

P.P.S: Yesterday was Perl's 15th birthday.  Happy birthday, Perl!