I've been looking for a script to do just that for quite some time now but, as I couldn't find anything that satisfied my needs, I thought I should port the java function that is available here. I would be happy to read any comments or suggestions for improvement. 

#!/usr/bin/perl --

print "Content-Type: text/html\n\n";

print "<html><head>";
print "<META HTTP-EQUIV='CONTENT-TYPE'";
print " CONTENT='text/html; charset=utf-8'>";
print "</head><body>";

&pair_split;

# Results can be manipulated here

print "</body></html>";

exit;

# Parse input -- Use POST method

sub pair_split{
  read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
  @pairs = split(/&/, $buffer);
  foreach $pair (@pairs) {
    local($name, $value) = split(/=/, $pair);
      if ($name =~ /\%/) {$strng = $name; &xxutf; $name = $sbuf;}
      if ($value =~ /\%/) {$strng = $value; &xxutf; $value = $sbuf;}
      $name =~ tr/+/ /;
      $name =~ tr/\0//d;
      $value =~ tr/+/ /;
      $value =~ tr/\0//d;
         
      $$name = $value;        # Assign values to $names
  }
}

# Decode XX-encoded letters to UTF-8

sub xxutf {
  $l = length($strng);
  $ch = -1;
  $b = 0;
  $sumb = 0;

  for ($i = 0, $more = -1; $i < $l; $i++) {

# Get next byte b from URL segment strng

    $ch = substr $strng, $i, 1;
    if ($ch eq '%') {
      $i++;
        $ch = substr $strng, $i, 1;
        $hb = ($ch =~ /[0-9]/)
          ? $ch - '0'
          : 10+(ord(lc$ch) - ord('a')) & 15;
        $i++;
        $ch =  substr $strng, $i, 1;
        $lb = ($ch =~ /[0-9]/)
          ? $ch - '0'
          : 10+(ord(lc$ch) - ord('a')) & 15;
        $b = ($hb << 4) | $lb;
    }
    elsif ($ch eq '+') {
        $b = ' ';
    }
    else {$b = $ch};
    
# Decode byte b as UTF-8, sumb collects incomplete chars


    if (($b & 192) == 128) {                   
                   # 10xxxxxx (continuation byte)
        $sumb = ($sumb << 6) | ($b & 63);    
                   # Add 6 bits to sumb
        if (--$more == 0) {
          $sumb = "&#" . $sumb;                 
                   # Create UTF-8 encoding
          $sumb = $sumb . ";";
          $sbuf = $sbuf . $sumb;               
                   # Add char to sbuf
        }                     
    }
    elsif (($b & 128) == 0) {                
                   # 0xxxxxxx (yields 7 bits)
      $sbuf = $sbuf . $b;                    
                   # Store in sbuf
    }
    elsif (($b & 224) == 192) {              
                   # 110xxxxx (yields 5 bits)
      $sumb = $b & 31;
      $more = 1;                             
                   # Expect 1 more byte
    }
    elsif (($b & 240) == 224) {               
                   # 1110xxxx (yields 4 bits)
      $sumb = $b & 15;
      $more = 2;                             
                   # Expect 2 more bytes
    }
    elsif (($b & 248) == 240) {               
                   # 11110xxx (yields 3 bits)
      $sumb = $b & 7;
      $more = 3;                             
                   # Expect 3 more bytes
    }
    elsif (($b & 252) == 248) {               
                   # 111110xx (yields 2 bits)
      $sumb = $b & 3;
      $more = 4;                             
                   # Expect 4 more bytes
    }
    else {                                      
                   # if ((b & 0xfe) == 0xfc)
      $sumb = $b & 1;                           
                   # 1111110x (yields 1 bit)
      $more = 5;                             
                   # Expect 5 more bytes
    }

# We don't test if the UTF-8 encoding is well-formed

  }
}

[download]

In reply to Perl script to transform XX-encoding to UTF-8 by emav

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.