Perl Quiz of the Week #23

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Write a program, 'parens', which gets a command line argument, n',
which is an integer.  The program should print all the
properly-balanced strings of parentheses of length 2n.  For example,
given the argument '3', the program should print these five lines:

        ((()))
        (()())
        (())()
        ()(())
        ()()()

in some order.  (The order is not important.)  

For the argument '1'; the output should be:
        
        ()

and for argument '4', the output should be:

        (((())))
        ((()()))
        ((())())
        ((()))()
        (()(()))
        (()()())
        (()())()
        (())(())
        (())()()
        ()((()))
        ()(()())
        ()(())()
        ()()(())
        ()()()()

in some order.

[ ADMIN: I'm still hoping someone will step forward to write a report
  about expert quiz #22.  - MJD ]