IMPORTANT: Please do not post solutions, hints, or other spoilers
        until at least 60 hours after the date of this message.
        Thanks.

IMPORTANTE: Por favor, no enviéis soluciones, pistas, o cualquier otra
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Qing3 Zhu4Yi4: Qing3 Ning2 Deng3Dao4 Jie1Dao4 Ben3 Xin4Xi2 Zhi1Hou4 60
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----------------------------------------------------------------

This quiz is phrased for Unix systems. If it makes sense to write a
solution for Windows or other systems, feel free to do so.

The usual way to look for a character string in files in Unix is to use
grep. For instance, let's say you want to search for the word 'summary'
without regard to case in all files in a certain directory. You might say:

grep -i summary *

But if there is a very large number of files in your directory, you will
get something like this:

ksh: /usr/bin/grep: arg list too long

Now, you could just issue multiple commands, like this:

grep -i summary [A-B]*
grep -i summary [C-E]*
etc.

... but that's so tedious. Write a Perl program that allows you to search
all files in such a directory with one command.

You're probably wondering:
- Should I use grep? egrep? fgrep? Perl's regex matching?
- Should there be an option to make the search case-sensitive or not?
- Should we traverse all files under all subdirectories?

You can decide for yourself on these questions. There is one other
requirement, though: the program must not fail when it finds things for
which grepping does not make sense (e.g. directories or named pipes).