For starters, I am not opening a file. I am receiving the utf8 input from an HTML form, and, quite frankly, I have no way of knowing whether user input will be received in the Perl script as utf8, unicode, big5, gb2312, etc., although I am trying to work solely with utf8. The database being searched is in utf8, but Perl is doing next to nothing with it once received with the DBI commands, other than outputting it back to HTML.

On your advice, I tried learning more about utf8, and have tried using the -COE command in the shebang line (this rendered the output unreadable), and I tried using the Encode qw(encode decode), to no avail.

Here are my current uses:

use CGI;
use CGI::Carp qw(fatalsToBrowser);
use strict;
use DBI;
use Encode;
use Encode qw(_utf8_on);
use Encode::HanConvert; #Module for dealing with CJK conversions
use Encode qw(encode decode);
require Encode::CN;
require Encode::TW;
[download]

The real puzzle, to me, is that split// seems to work, but the s/// won't work. Unfortunately, I have no way of knowing how many terms the user will be entering, so using split would require some significant recoding. Thank you!

If you don't know the encoding of data, how shall perl know it?

When you don't set CGIs charset parameter, it will return a byte string, that you have to convert to perl's internal format... but I wrote that already.

You can try to use Encode::Guess if you have a few possible charsets that aren't too similar and your input data is long enough.

If this doesn't hold true you have to take care that your input will be in a known encoding, for example in HTML forms you can set the accept-charset attribute to utf8 only.

And when you want unicode semantics in regex matches, check with encode::is_utf8($string) that it is indeed in perl's internal format.

---

Perl 6 in German

"the" internal format for Unicode strings is actually two different formats: ISO-8859-1 and UTF8. As an optimization, Perl may use ISO-8859-1 even though the original source was UTF-8.

Encode::_is_utf8 (not encode::is_utf8) will return true if the string is internally encoded as UTF8, and can return false even though you properly decoded.

Recommendation: do not look at the UTF8 flag. It is next to useless, except for internals debugging and performance tweaking.

Pretend that the UTF8 flag does not exist.

Do not use Encode::_is_utf8 (it is prefixed with an underscore for a reason: you should not have to use this in normal code).

Really, Perl's Unicode strings may be encoded as *ANYTHING* internally. Don't look at the internal buffer, unless you really want to mess with the internals. You do not need to know the internals for simple text processing, as is the case in the OP's problem.

Well, I'm stumped. The program will match the spaces properly when doing a split// but not when doing a s///. I have now set the attribute on the HTML form to UTF8. I have inserted the code posted earlier, and still nothing. So, to demonstrate the exact conundrum I am up against, I have reduced my code to just the barest essentials for testing this UTF8 regex.

Please feel free to try this script on your own server to see if you can get it to work properly on Chinese fonts. I have included a sample Chinese phrase in the script which you should be able to copy and paste into it for testing purposes. Compare it with an English search, and you'll see why I'm frustrated!

#!/usr/bin/perl -wT -CE
use Encode;
use Encode qw(_utf8_on);
use Encode qw(encode decode);

##### PARSE THE FORM INPUT
    if ($ENV{CONTENT_LENGTH}) {
        read(STDIN, $buffer, $ENV{CONTENT_LENGTH});
        @pairs = split(/&/,$buffer);
    } else {
        $buffer = $ENV{QUERY_STRING};
        @pairs = split(/\+/,$buffer);
    }
    foreach $pair (@pairs) {
        ($name, $value) = split(/=/,$pair);
        $value =~ tr/+/ /;
        $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C",hex($1))/eg;
        $input{$name} = $value;
    }
  $terms=$input{terms}; 

##### START TESTING PHASE
print "Content-type: text/html\n\n";
print "TERMS: $terms";

##### TRY A SPLIT
($a, $b, $c, $d, $e, $f) = split/\p{IsSpace}/, $terms;
print "<p>A:$a:<p>B:$b:<p>C:$c:<p>D:$d:<p>E:$e:<p>F:$f:\n";

##### NOW TRY A SUBSTITUTION
$word = qr/\b(?!(?:AND|OR|XOR|NOT)\b)\w+/i;
$terms =~ s/($word)\p{IsSpace}*($word)/$1 AND $2/g for 1..2;
print "<p>Terms:$terms\n";

##### PRINT THE WEBPAGE
print <<HTML;
<html lang=utf8>
<head>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf8">
<title>SEARCH</title>
</head><body>
<h1 align="center">Search</h1>
<form name="ff" method="POST" accept-encoding="UTF-8" 
                accept-charset="utf-8" action="$0">
Search terms: 
<input type="text" size="40" name="terms" value="$terms"></input>
<p>An example Chinese phrase: &#32102;&#32842; &#22825;&#23460;&#25152
+; &#26377;&#25104;&#21729;
<input type="submit" name="submit" value="Submit"></input>
</form></body></html>
HTML
[download]

For those who may be seeking the same wisdom, I would like to post the full solution in my case.

My entire "use" section:

use CGI;
use CGI::Carp qw(fatalsToBrowser);
use strict;
use DBI;
use Encode;
use Encode::HanConvert; #Module for dealing with CJK conversions
use Encode qw(encode decode);
use POSIX qw(locale_h);
require Encode::CN;
require Encode::TW;
require 5.004;
[download]

$name = decode("utf-8", $name); 
$value = decode("utf-8", $value);
[download]

my $quest = $dbh->prepare($statement, { RaiseError => 1 }) 
       or die "Cannot prepare statement! $DBI::errstr\n";
while(@row = $quest->fetchrow_array()) {
  $c1=shift @row;
  $c1=decode("utf-8", $c1);
  ...
}
[download]

$line =~ s%(?:\p{IsSpace}*) #Match zero or more spaces
(\bNOT)?                    #Match zero or one "NOT" operator(s)
(\(*)                       #Match zero or more left parentheses
(\p{IsSpace}*|\s*|\b|^)     #Match zero+ spaces or a word boundary
(?!\")                      #Ensure this doesn't appear beforehand
((?:\p{IsWord}|\w|`|        #Match zero+ words
(?:\&\p{IsAlnum}*\;)*)*     #Include HTML special chars, e.g. á
(?:\.\{\d+\})*              #Include zero+ MySQL-style wildcard '?'s
(?:\[\.[^\.\]]*\.\])*       #Include zero+ MySQL REGEXP chars
(?:\[\:[^\:\]]*\:\])*       #Include zero+ MySQL REGEXP special chars
(?:\[[^\]]*\])*             #Incl. zero+ MySQL REGEXP special patterns
(?:\*(?!\"))*               #Include zero+ stand-alone asterisks
(?:\%(?!\"))*  )            #Include zero+ stand-alone percent signs
(?:\s*|\p{IsSpace}*)        #Match zero+ spaces
(\)*)                       #Match zero+ right parentheses
(?:\p{IsSpace}|\s)*         #Match zero+ spaces
(["()]*)                    #Match zero+ double quotes or parentheses
(?:\p{IsSpace}*)            #Match zero+ spaces
(                           #(begin group)
  (?:NOT|OR|AND|XOR)*       #Match zero+ operator words
  (?:\p{IsSpace}+|\(+|\p{IsZ}|\Z) #Then one+ spaces OR one+ ")"
                                  #OR end-of-string
)                           #(end group)
                            #AND SUBSTITUTE THE ABOVE WITH THE BELOW
%$2$3$table\.$columnName`$1`$like`"$l$wb$4$we$l"$5$6 $7 %xig;
[download]

~Polyglot~

That "use 5.004" is useless; Encode already requires 5.8. I recommend using "use 5.8.3;" or "use 5.008003";