Perl Documentation: The Key to Perl

Perm URL with updates:

So, i wanted to know what the option perl -C does. So, here's perldoc perlrun. Excerpt:

    -C [*number/list*]
         The -C flag controls some of the Perl Unicode features.

         As of 5.8.1, the -C can be followed either by a number or a list of
         option letters. The letters, their numeric values, and effects are
         as follows; listing the letters is equal to summing the numbers.

             I     1   STDIN is assumed to be in UTF-8
             O     2   STDOUT will be in UTF-8
             E     4   STDERR will be in UTF-8
             S     7   I + O + E
             i     8   UTF-8 is the default PerlIO layer for input streams
             o    16   UTF-8 is the default PerlIO layer for output streams
             D    24   i + o
             A    32   the @ARGV elements are expected to be strings encoded
                       in UTF-8
             L    64   normally the "IOEioA" are unconditional,
                       the L makes them conditional on the locale environment
                       variables (the LC_ALL, LC_TYPE, and LANG, in the order
                       of decreasing precedence) -- if the variables indicate
                       UTF-8, then the selected "IOEioA" are in effect
             a   256   Set ${^UTF8CACHE} to -1, to run the UTF-8 caching code in
                       debugging mode.

         For example, -COE and -C6 will both turn on UTF-8-ness on both
         STDOUT and STDERR. Repeating letters is just redundant, not
         cumulative nor toggling.

         The "io" options mean that any subsequent open() (or similar I/O
         operations) in the current file scope will have the ":utf8" PerlIO
         layer implicitly applied to them, in other words, UTF-8 is expected
         from any input stream, and UTF-8 is produced to any output stream.
         This is just the default, with explicit layers in open() and with
         binmode() one can manipulate streams as usual.

         -C on its own (not followed by any number or option list), or the
         empty string "" for the "PERL_UNICODE" environment variable, has
         the same effect as -CSDL. In other words, the standard I/O handles
         and the default "open()" layer are UTF-8-fied *but* only if the
         locale environment variables indicate a UTF-8 locale. This
         behaviour follows the *implicit* (and problematic) UTF-8 behaviour
         of Perl 5.8.0.

         You can use -C0 (or "0" for "PERL_UNICODE") to explicitly disable
         all the above Unicode features.

         The read-only magic variable "${^UNICODE}" reflects the numeric
         value of this setting. This variable is set during Perl startup and
         is thereafter read-only. If you want runtime effects, use the
         three-arg open() (see "open" in perlfunc), the two-arg binmode()
         (see "binmode" in perlfunc), and the "open" pragma (see open).

         (In Perls earlier than 5.8.1 the -C switch was a Win32-only switch
         that enabled the use of Unicode-aware "wide system call" Win32
         APIs. This feature was practically unused, however, and the command
         line switch was therefore "recycled".)

         Note: Since perl 5.10.1, if the -C option is used on the "#!" line,
         it must be specified on the command line as well, since the
         standard streams are already set up at this point in the execution
         of the perl interpreter. You can also use binmode() to set the
         encoding of an I/O stream.

reading that is like a adventure. It's like this:

The -C is a key to unlock many secrets. Just get it, and you'll be all
good to go, except in cases you may need the inner key. You'll find a
hinge in the key, open it, then there's a subkey. On the subkey,
there's a number. Take that number to the lock, it will open with
keyX. When you use keyX, it must be matched with the previous inner
key with 8th bit. keyX doesn't have a ID, but you can make one by
finding the number at the place you found the key C. Key C is actually
optional, but when inner key and keyX's number matches, it changes the
nature of the lock. This is when you need to turn on keyMode …

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