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       Perl::Critic::Policy::InputOutput::RequireEncodingWithUTF8Layer - Write "open $fh,
       q{<:encoding(UTF-8)}, $filename;" instead of "open $fh, q{{<:utf8}, $filename;".

       This Policy is part of the core Perl::Critic distribution.

       Use of the ":utf8" I/O layer (as opposed to ":encoding(UTF8)" or ":encoding(UTF-8)") was
       suggested in the Perl documentation up to version 5.8.8. This may be OK for output, but on
       input ":utf8" does not validate the input, leading to unexpected results.

       An exploit based on this behavior of ":utf8" is exhibited on PerlMonks at
       <http://www.perlmonks.org/?node_id=644786>. The exploit involves a string read from an
       external file and sanitized with "m/^(\w+)$/", where $1 nonetheless ends up containing
       shell meta-characters.

       To summarize:

	open $fh, '<:utf8', 'foo.txt';		   # BAD
	open $fh, '<:encoding(UTF8)', 'foo.txt';   # GOOD
	open $fh, '<:encoding(UTF-8)', 'foo.txt';  # BETTER

       See the Encode documentation for the difference between "UTF8" and "UTF-8". The short
       version is that "UTF-8" implements the Unicode standard, and "UTF8" is liberalized.

       For consistency's sake, this policy checks files opened for output as well as input, For
       complete coverage it also checks "binmode()" calls, where the direction the operation can
       not be determined.

       This Policy is not configurable except for the standard options.

       Because "Perl::Critic" does a static analysis, this policy can not detect cases like

	my $encoding = ':utf8';
	binmode $fh, $encoding;

       where the encoding is computed.



       "perldoc -f binmode"



       Thomas R. Wyant, III wyant at cpan dot org

       Copyright (c) 2010-2011 Thomas R. Wyant, III

       This program is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.

perl v5.16.3		       Perl::Critic::Policy::InputOutput::RequireEncodingWithUTF8Layer(3)
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