PerlBroker has asked for the wisdom of the Perl Monks concerning the following question:

I have this error, and although, once this script worked, I cannot myself figure out what to do: 
Cannot decode string with wide characters at /usr/lib/perl/5.10/Encode
+.pm line 174.

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My input is UTF-8 from the HTML form, and the script is roughly this one: 
#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use CGI qw(-utf8);
use Encode;
use encoding 'utf8';
use CGI::Carp qw(croak fatalsToBrowser);
# etc...

$| = 1;
binmode(STDOUT, ":utf8");
binmode(STDIN, ":utf8");

my $q = new CGI;
croak("It works yet...");
my $referer_url = "@{[ $q->url ]}";
croak("Cannot decode string... error before this line.");

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In general, if a value from the HTML textform contains one UTF-8 character, I get that error. Any help is appreciated.

Replies are listed 'Best First'.
Re: Help for "Cannot decode string with wide characters..." and CGI.pm
by moritz (Cardinal) on Apr 08, 2012 at 16:09 UTC
    When you use utf8;, then your string literals are text strings. But this 
    my $referer_url = "@{[ $q->url ]}";

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    tries to interpolate an URL, and that seems to be a byte string. Simply mixing those two is a very bad idea.

    I don't see why you do it in this complicated way anyway. What's wrong with 

    my $url = $q->url;

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    or maybe 

    my $url = decode_utf8 $q->url;

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    depending on how you want to use it.

    Perl 6 - second systems done right
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Re: Help for "Cannot decode string with wide characters..." and CGI.pm
by Anonymous Monk on Apr 08, 2012 at 11:04 UTC

    upgrade Encode CGI Encoding   cpanp -i Encode CGI Encoding

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      After upgrade of Encode and CGI, it started working, at least there is no error. But now I get these characters in messages: ��
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        Maybe something like this: 
        #!/usr/bin/perl -l

BEGIN { $| = 1;}

use strict;
use warnings;
use utf8;
use Encode;
use CGI qw/:standard -utf8/;
use CGI::Carp qw/fatalsToBrowser set_message/;
$CGI::PARAM_UTF8 = 1;

BEGIN {
    sub handle_errors {
        my $msg = shift;
        print "<h1>There's a problem</h1>";
        print "<p>Cannot decode string: $msg</p>";
    }
    set_message(\&handle_errors);
}

my $q = CGI->new;
binmode STDOUT, ":encoding(UTF-8)";
my $referer_url = "@{[ $q->url ];}";
print $referer_url;

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Re: Help for "Cannot decode string with wide characters..." and CGI.pm
by ikegami (Patriarch) on Apr 10, 2012 at 00:34 UTC

    Get rid of 

    binmode(STDIN, ":utf8");

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    Your corrupting the data stream passed to CGI. The proper way to decode the parameters is using 

    use CGI qw(-utf8);

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    which you already use. Speaking of doing the same thing twice, you did *that* twice too! First you tell Perl the source code is UTF-8 

    use utf8;

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    then you tell it again using a buggy version of the first method. 

    use encoding 'utf8';

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    The encoding is UTF-8, by the way. utf8 is something else.

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